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  • Occasional "Could not load file or assembly" in asmx WebService on IIS and DFS

    - by user8804
    We have a handfull of ASMX web service hosted on two identical Windows Server 2003 boxes. The virtual directory for the web services is loaded in a DFS share, both servers point to the same share. We have a load balancer between the internet and the two web servers. At a seemingly random interval (right now about twice per week) when a user tries to access a method on the web service, IIS returns the error: "Could not load file or assembly" for one of the assemblies used in the method call, and will continue reporting it each time the method is called until the app pool is recycled. We haven't found any distinguishable pattern to the problem. This is what I know: the missing assembly varies (but it's always a home-brew assembly) the Web Service method that fails varies there is no noticeable pattern to the times or intervals where the problem appears there are no admin users accessing the servers when the problem appears the failing method will work correctly on one server and fail on the other, even though both point to the same bin folder the problem can always be corrected by recycling the app pool and making no other changes I have enabled the Assembly Binder Log, and know that the binder is looking in the correct location for the file. Our assemblies are compiled for .Net 3.5.

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  • Unexpected results from custom partitioning scheme - Ubuntu preseed unattended install

    - by Mark Renouf
    Hi... I need some help with partman-auto custom recipe in preseed.... it's doing unexpected things, the docs aren't so clear. This is in my preseed file: d-i partman-auto/expert_recipe string \ boot-root-var :: \ 1024 100 1024 ext4 \ $primary{ } $bootable{ } \ method{ format } format{ } \ use_filesystem{ } filesystem{ ext4 } \ mountpoint{ /boot } \ . \ 2048 50 4096 ext4 \ method{ format } format{ } \ use_filesystem{ } filesystem{ ext4 } \ mountpoint{ / } \ . \ 4096 25 100000 ext4 \ method{ format } format{ } \ use_filesystem{ } filesystem{ ext4 } \ mountpoint{ /var } \ . \ 256 75 100% linux-swap \ method{ swap } format{ } \ . Given an 80GB drive. I ended up with these partitions: / 2GB /boot 1GB /var 4GB swap 72GB What went wrong? What I want is: / 2GB /boot 1GB /var 72GB swap 4GB

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  • Preseeding Ubuntu partman recipe using LVM and RAID

    - by Swav
    I'm trying to preseed Ubuntu 12.04 server installation and created a recipe that would create RAID 1 on 2 drives and then partition that using LVM. Unfortunately partman complains when creating LVM volumes saying there no partitions in recipe that could be used with LVM (in console it complains about unusable recipe). The layout I'm after is RAID 1 on sdb and sdc (installing from USB stick so it takes sda) and then use LVM to create boot, root and swap. The odd thing is that if I change the mount point of boot_lv to home the recipe works fine (apart from mounting in wrong place), but when mounting at /boot it fails I know I could use separate /boot primary partition, but can anybody tell me why it fails. Recipe and relevant options below. ## Partitioning using RAID d-i partman-auto/disk string /dev/sdb /dev/sdc d-i partman-auto/method string raid d-i partman-lvm/device_remove_lvm boolean true d-i partman-md/device_remove_md boolean true #d-i partman-lvm/confirm boolean true d-i partman-auto-lvm/new_vg_name string main_vg d-i partman-auto/expert_recipe string \ multiraid :: \ 100 512 -1 raid \ $lvmignore{ } \ $primary{ } \ method{ raid } \ . \ 256 512 256 ext3 \ $defaultignore{ } \ $lvmok{ } \ method{ format } \ format{ } \ use_filesystem{ } \ filesystem{ ext3 } \ mountpoint{ /boot } \ lv_name{ boot_lv } \ . \ 2000 5000 -1 ext4 \ $defaultignore{ } \ $lvmok{ } \ method{ format } \ format{ } \ use_filesystem{ } \ filesystem{ ext4 } \ mountpoint{ / } \ lv_name{ root_lv } \ . \ 64 512 300% linux-swap \ $defaultignore{ } \ $lvmok{ } \ method{ swap } \ format{ } \ lv_name{ swap_lv } \ . d-i partman-auto-raid/recipe string \ 1 2 0 lvm - \ /dev/sdb1#/dev/sdc1 \ . d-i mdadm/boot_degraded boolean true #d-i partman-md/confirm boolean true #d-i partman-partitioning/confirm_write_new_label boolean true #d-i partman/choose_partition select Finish partitioning and write changes to disk #d-i partman/confirm boolean true #d-i partman-md/confirm_nooverwrite boolean true #d-i partman/confirm_nooverwrite boolean true EDIT: After a bit of googling I found below snippet of code from partman-auto-lvm, but I still don't understand why would they prevent that setup if it's possible to do manually and booting from boot partition on LVM is possible. # Make sure a boot partition isn't marked as lvmok if echo "$scheme" | grep lvmok | grep -q "[[:space:]]/boot[[:space:]]"; then bail_out unusable_recipe fi

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  • Occasional "Could not load file or assembly" in asmx WebService on IIS and DFS

    - by jesse-mcdowell
    We have a handfull of ASMX web service hosted on two identical Windows Server 2003 boxes. The virtual directory for the web services is loaded in a DFS share, both servers point to the same share. We have a load balancer between the internet and the two web servers. At a seemingly random interval (right now about twice per week) when a user tries to access a method on the web service, IIS returns the error: "Could not load file or assembly" for one of the assemblies used in the method call, and will continue reporting it each time the method is called until the app pool is recycled. We haven't found any distinguishable pattern to the problem. This is what I know: the missing assembly varies (but it's always a home-brew assembly) the Web Service method that fails varies there is no noticeable pattern to the times or intervals where the problem appears there are no admin users accessing the servers when the problem appears the failing method will work correctly on one server and fail on the other, even though both point to the same bin folder the problem can always be corrected by recycling the app pool and making no other changes I have enabled the Assembly Binder Log, and know that the binder is looking in the correct location for the file. Our assemblies are compiled for .Net 3.5.

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  • All Xen domU LVM volumes corrupt after reboot

    - by zcs
    I'm running a Debian Squeeze dom0, and after rebooting it all 7 of my domUs have data corruption. Each is setup as ext3 partition directly on a separate lvm2 volume. None of the lvm volumes will mount; all have bad superblocks. I've tried e2fsck with each superblock to no avail. What else can I try? Each domU has two LVM volumes connected to it, one for the disk and one for swap. The disk is mounted at root, formatted as a normal ext3 partition as a xen-blk device. The volumes are never mounted outside of the guest OS. I'm running Ubuntu 11.04 using the instructions here. I'm not sure that they didn't shutdown properly, all I know is they were corrupt after I issues a clean 'reboot' on the dom0. Here's a sample Xen config file; the rest are the same except for name, vcpus, memory, vif and disk. name = 'load1' vcpus = 2 memory = 512 vif = ['bridge=prbr0', 'bridge=eth0'] disk = ['phy:/dev/VolGroup00/load1-disk,xvda,w','phy:/dev/VolGroup00/load1-swap,xvdb,w'] #============================================================================ # Debian Installer specific variables def check_bool(name, value): value = str(value).lower() if value in ('t', 'tr', 'tru', 'true'): return True return False global var_check_with_default def var_check_with_default(default, var, val): if val: return val return default xm_vars.var('install', use='Install Debian, default: false', check=check_bool) xm_vars.var("install-method", use='Installation method to use "cdrom" or "network" (default: network)', check=lambda var, val: var_check_with_default('network', var, val)) # install-method == "network" xm_vars.var("install-mirror", use='Debian mirror to install from (default: http://archive.ubuntu.com/ubuntu)', check=lambda var, val: var_check_with_default('http://archive.ubuntu.com/ubuntu', var, val)) xm_vars.var("install-suite", use='Debian suite to install (default: natty)', check=lambda var, val: var_check_with_default('natty', var, val)) # install-method == "cdrom" xm_vars.var("install-media", use='Installation media to use (default: None)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-cdrom-device", use='Installation media to use (default: xvdd)', check=lambda var, val: var_check_with_default('xvdd', var, val)) # Common options xm_vars.var("install-arch", use='Debian mirror to install from (default: amd64)', check=lambda var, val: var_check_with_default('amd64', var, val)) xm_vars.var("install-extra", use='Extra command line options (default: None)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-installer", use='Debian installer to use (default: network uses install-mirror; cdrom uses /install.ARCH)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-kernel", use='Debian installer kernel to use (default: uses install-installer)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.var("install-ramdisk", use='Debian installer ramdisk to use (default: uses install-installer)', check=lambda var, val: var_check_with_default(None, var, val)) xm_vars.check() if not xm_vars.env.get('install'): bootloader="/usr/sbin/pygrub" elif xm_vars.env['install-method'] == "network": import os.path print "Install Mirror: %s" % xm_vars.env['install-mirror'] print "Install Suite: %s" % xm_vars.env['install-suite'] if xm_vars.env['install-installer']: installer = xm_vars.env['install-installer'] else: installer = xm_vars.env['install-mirror']+"/dists/"+xm_vars.env['install-suite'] + \ "/main/installer-"+xm_vars.env['install-arch']+"/current/images" print "Installer: %s" % installer print print "WARNING: Installer kernel and ramdisk are not authenticated." print if xm_vars.env.get('install-kernel'): kernelurl = xm_vars.env['install-kernel'] else: kernelurl = installer + "/netboot/xen/vmlinuz" if xm_vars.env.get('install-ramdisk'): ramdiskurl = xm_vars.env['install-ramdisk'] else: ramdiskurl = installer + "/netboot/xen/initrd.gz" import urllib class MyUrlOpener(urllib.FancyURLopener): def http_error_default(self, req, fp, code, msg, hdrs): raise IOError("%s %s" % (code, msg)) urlopener = MyUrlOpener() try: print "Fetching %s" % kernelurl kernel, _ = urlopener.retrieve(kernelurl) print "Fetching %s" % ramdiskurl ramdisk, _ = urlopener.retrieve(ramdiskurl) except IOError, _: raise elif xm_vars.env['install-method'] == "cdrom": arch_path = { 'i386': "/install.386", 'amd64': "/install.amd" } if xm_vars.env['install-media']: print "Install Media: %s" % xm_vars.env['install-media'] else: raise OptionError("No installation media given.") if xm_vars.env['install-installer']: installer = xm_vars.env['install-installer'] else: installer = arch_path[xm_vars.env['install-arch']] print "Installer: %s" % installer if xm_vars.env.get('install-kernel'): kernelpath = xm_vars.env['install-kernel'] else: kernelpath = installer + "/xen/vmlinuz" if xm_vars.env.get('install-ramdisk'): ramdiskpath = xm_vars.env['install-ramdisk'] else: ramdiskpath = installer + "/xen/initrd.gz" disk.insert(0, 'file:%s,%s:cdrom,r' % (xm_vars.env['install-media'], xm_vars.env['install-cdrom-device'])) bootloader="/usr/sbin/pygrub" bootargs="--kernel=%s --ramdisk=%s" % (kernelpath, ramdiskpath) print "From CD" else: print "WARNING: Unknown install-method: %s." % xm_vars.env['install-method'] if xm_vars.env.get('install'): # Figure out command line if xm_vars.env['install-extra']: extras=[xm_vars.env['install-extra']] else: extras=[] # Reboot will just restart the installer since this file is not # reparsed, so halt and restart that way. extras.append("debian-installer/exit/always_halt=true") extras.append("--") extras.append("quiet") console="hvc0" try: if len(vfb) >= 1: console="tty0" except NameError, e: pass extras.append("console="+ console) extra = str.join(" ", extras) print "command line is \"%s\"" % extra root There are two LVM logical volumes connected to each VM. Here's the fdisk -l output for the disk volume: Disk /dev/VolGroup00/VMNAME-disk: 8589 MB, 8589934592 bytes 255 heads, 63 sectors/track, 1044 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00029c01 Device Boot Start End Blocks Id System /dev/VolGroup00/VMNAME-disk1 1 1045 8386560 83 Linux And the swap volume: Disk /dev/VolGroup00/VMNAME-swap: 536 MB, 536870912 bytes 37 heads, 35 sectors/track, 809 cylinders Units = cylinders of 1295 * 512 = 663040 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0004faae Device Boot Start End Blocks Id System /dev/VolGroup00/VMNAME-swap1 2 809 522240 82 Linux swap / Solaris Partition 1 has different physical/logical beginnings (non-Linux?): phys=(0, 32, 33) logical=(1, 21, 19) Partition 1 has different physical/logical endings: phys=(65, 36, 35) logical=(808, 4, 28)

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  • puppet master REST API returns 403 when running under passenger works when master runs from command line

    - by Anadi Misra
    I am using the standard auth.conf provided in puppet install for the puppet master which is running through passenger under Nginx. However for most of the catalog, files and certitifcate request I get a 403 response. ### Authenticated paths - these apply only when the client ### has a valid certificate and is thus authenticated # allow nodes to retrieve their own catalog path ~ ^/catalog/([^/]+)$ method find allow $1 # allow nodes to retrieve their own node definition path ~ ^/node/([^/]+)$ method find allow $1 # allow all nodes to access the certificates services path ~ ^/certificate_revocation_list/ca method find allow * # allow all nodes to store their reports path /report method save allow * # unconditionally allow access to all file services # which means in practice that fileserver.conf will # still be used path /file allow * ### Unauthenticated ACL, for clients for which the current master doesn't ### have a valid certificate; we allow authenticated users, too, because ### there isn't a great harm in letting that request through. # allow access to the master CA path /certificate/ca auth any method find allow * path /certificate/ auth any method find allow * path /certificate_request auth any method find, save allow * path /facts auth any method find, search allow * # this one is not stricly necessary, but it has the merit # of showing the default policy, which is deny everything else path / auth any Puppet master however does not seems to be following this as I get this error on client [amisr1@blramisr195602 ~]$ sudo puppet agent --no-daemonize --verbose --server bangvmpllda02.XXXXX.com [sudo] password for amisr1: Starting Puppet client version 3.0.1 Warning: Unable to fetch my node definition, but the agent run will continue: Warning: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /certificate_revocation_list/ca [find] at :110 Info: Retrieving plugin Error: /File[/var/lib/puppet/lib]: Failed to generate additional resources using 'eval_generate: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /file_metadata/plugins [search] at :110 Error: /File[/var/lib/puppet/lib]: Could not evaluate: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /file_metadata/plugins [find] at :110 Could not retrieve file metadata for puppet://devops.XXXXX.com/plugins: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /file_metadata/plugins [find] at :110 Error: Could not retrieve catalog from remote server: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /catalog/blramisr195602.XXXXX.com [find] at :110 Using cached catalog Error: Could not retrieve catalog; skipping run Error: Could not send report: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /report/blramisr195602.XXXXX.com [save] at :110 and the server logs show XX.XXX.XX.XX - - [10/Dec/2012:14:46:52 +0530] "GET /production/certificate_revocation_list/ca? HTTP/1.1" 403 102 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:52 +0530] "GET /production/file_metadatas/plugins?links=manage&recurse=true&&ignore=---+%0A++-+%22.svn%22%0A++-+CVS%0A++-+%22.git%22&checksum_type=md5 HTTP/1.1" 403 95 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:52 +0530] "GET /production/file_metadata/plugins? HTTP/1.1" 403 93 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:53 +0530] "POST /production/catalog/blramisr195602.XXXXX.com HTTP/1.1" 403 106 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:53 +0530] "PUT /production/report/blramisr195602.XXXXX.com HTTP/1.1" 403 105 "-" "Ruby" thefile server conf file is as follows (and goin by what they say on puppet site, It is better to regulate access in auth.conf for reaching file server and then allow file server to server all) [files] path /apps/puppet/files allow * [private] path /apps/puppet/private/%H allow * [modules] allow * I am using server and client version 3 Nginx has been compiled using the following options nginx version: nginx/1.3.9 built by gcc 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC) TLS SNI support enabled configure arguments: --prefix=/apps/nginx --conf-path=/apps/nginx/nginx.conf --pid-path=/apps/nginx/run/nginx.pid --error-log-path=/apps/nginx/logs/error.log --http-log-path=/apps/nginx/logs/access.log --with-http_ssl_module --with-http_gzip_static_module --add-module=/usr/lib/ruby/gems/1.8/gems/passenger-3.0.18/ext/nginx --add-module=/apps/Downloads/nginx/nginx-auth-ldap-master/ and the standard nginx puppet master conf server { ssl on; listen 8140 ssl; server_name _; passenger_enabled on; passenger_set_cgi_param HTTP_X_CLIENT_DN $ssl_client_s_dn; passenger_set_cgi_param HTTP_X_CLIENT_VERIFY $ssl_client_verify; passenger_min_instances 5; access_log logs/puppet_access.log; error_log logs/puppet_error.log; root /apps/nginx/html/rack/public; ssl_certificate /var/lib/puppet/ssl/certs/bangvmpllda02.XXXXXX.com.pem; ssl_certificate_key /var/lib/puppet/ssl/private_keys/bangvmpllda02.XXXXXX.com.pem; ssl_crl /var/lib/puppet/ssl/ca/ca_crl.pem; ssl_client_certificate /var/lib/puppet/ssl/certs/ca.pem; ssl_ciphers SSLv2:-LOW:-EXPORT:RC4+RSA; ssl_prefer_server_ciphers on; ssl_verify_client optional; ssl_verify_depth 1; ssl_session_cache shared:SSL:128m; ssl_session_timeout 5m; } Puppet is picking up the correct settings from the files mentioned because config print command points to /etc/puppet [amisr1@bangvmpllDA02 puppet]$ sudo puppet config print | grep conf async_storeconfigs = false authconfig = /etc/puppet/namespaceauth.conf autosign = /etc/puppet/autosign.conf catalog_cache_terminus = store_configs confdir = /etc/puppet config = /etc/puppet/puppet.conf config_file_name = puppet.conf config_version = "" configprint = all configtimeout = 120 dblocation = /var/lib/puppet/state/clientconfigs.sqlite3 deviceconfig = /etc/puppet/device.conf fileserverconfig = /etc/puppet/fileserver.conf genconfig = false hiera_config = /etc/puppet/hiera.yaml localconfig = /var/lib/puppet/state/localconfig name = config rest_authconfig = /etc/puppet/auth.conf storeconfigs = true storeconfigs_backend = puppetdb tagmap = /etc/puppet/tagmail.conf thin_storeconfigs = false I checked the firewall rules on this VM; 80, 443, 8140, 3000 are allowed. Do I still have to tweak any specifics to auth.conf for getting this to work?

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  • Is there a debian lenny patch to allow apt-get to work with sftp?

    - by MiniQuark
    I would like to write things like this in /etc/apt/sources.list: deb sftp://[email protected]/path other stuff When I try this, apt-get complains that there is no sftp method for apt: # apt-get update E: The method driver /usr/lib/apt/methods/sftp could not be found. Has anyone written a patch to add the sftp method for apt? All I could find in Google was this spec for Ubuntu. Thanks for your help.

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  • Linux RHEL : Making disk image efficiently

    - by TheProfoundGeek
    I have a linux box having RHEL. Its disk (hda1) is having free space of about 25GB. I have an another disk (hda2) which is of 250GB having another RHEL instance, it's partitioned for 200GB. Data on the disk occupies about 21GB of data. The image of hda2 needs to be taken and restored on other disk of same specs. What is the best way to make image file of the hda2? Ideally the images size should be around 25GBs as the actual data on the disk is just 21GB. I am aware about the following two methods. Method 1 : Raw Image dd if=/dev/hda2 of=/path/to/image dd if=/path/to/image of=/dev/hda3 Question 1 : Will the above method make a gigantic image of 250GBs? Is it efficient? Method 2 : Compressed Image. dd if=/dev/hda2 | gzip > /path/to/image.gz gzip -dc /path/to/image.gz | dd of=/dev/hda2 Question 2 : I tried the method 2, its taking too long. What are the pit falls of this methods? Which of the above method id efficient and why? Is there any other Linux utility which can do the job? Third party tools are no no.

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  • Filtering in a HierarchicalDataTemplate via MarkupExtension?

    - by Dan Bryant
    I'm trying to create a MarkupExtension to allow filtering of items in an ItemsSource of a HierarchicalDataTemplate. In particular, I'd like to be able to supply a method name that will be executed on the DataContext in order to perform the filtering. The usage syntax I'm after looks like this: <HierarchicalDataTemplate DataType="{x:Type src:DeviceBindingViewModel}" ItemsSource="{Utilities:FilterCollection {Binding Definition.Entries}, MethodName=FilterEntries}"> <StackPanel Orientation="Horizontal"> <Image Source="{StaticResource BindingImage}" Width="24" Height="24" Margin="3"/> <TextBlock Text="{Binding DisplayName}" FontSize="12" VerticalAlignment="Center"/> </StackPanel> </HierarchicalDataTemplate> My code for the custom MarkupExtension looks like this: public sealed class FilterCollectionExtension : MarkupExtension { private readonly MultiBinding _binding; private Predicate<Object> _filterMethod; public string MethodName { get; set; } public FilterCollectionExtension(Binding binding) { _binding = new MultiBinding(); _binding.Bindings.Add(binding); //We package a reference to the DataContext with the binding so that the Converter has access to it var selfBinding = new Binding {RelativeSource = RelativeSource.Self}; _binding.Bindings.Add(selfBinding); _binding.Converter = new InternalConverter(this); } public FilterCollectionExtension(Binding binding, string methodName) : this(binding) { MethodName = methodName; } public override object ProvideValue(IServiceProvider serviceProvider) { return _binding; } private bool FilterInternal(Object dataContext, Object value) { //Filtering is only applicable if a DataContext is defined if (dataContext != null) { if (_filterMethod == null) { var type = dataContext.GetType(); var method = type.GetMethod(MethodName, new[] { typeof(Object) }); if (method == null || method.ReturnType != typeof(bool)) throw new InvalidOperationException("Could not locate a filter predicate named " + MethodName + " on the DataContext"); _filterMethod = (Predicate<Object>)Delegate.CreateDelegate(typeof(Predicate<Object>), dataContext, method); } else { if (_filterMethod.Target != dataContext) { _filterMethod = (Predicate<Object>) Delegate.CreateDelegate(typeof (Predicate<Object>), dataContext, _filterMethod.Method); } } if (_filterMethod != null) return _filterMethod(value); } //If no filtering resolved, just allow all elements return true; } private class InternalConverter : IMultiValueConverter { private readonly FilterCollectionExtension _owner; public InternalConverter(FilterCollectionExtension owner) { _owner = owner; } public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture) { var enumerable = values[0]; var targetElement = (FrameworkElement)values[1]; var view = CollectionViewSource.GetDefaultView(enumerable); view.Filter = item => _owner.FilterInternal(targetElement.DataContext, item); return view; } public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture) { throw new NotSupportedException("Cannot convert back"); } } } I can see that the extension is instantiated and I can see it return the MultiBinding that is used by the Template. I also see the call to the InternalConverter.Convert method, which sees the expected parameters (I see the collection provided by the nested {Binding}) and is successfully able to retrieve the ICollectionView for the incoming collection. The only problem is that FilterInternal never gets called. The template is ultimately being used by a TreeView, if that's relevant. I haven't been able to figure out why the FilterInternal method is not being called and I was hoping somebody might be able to offer some insight.

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  • exception creating a JDBC Conection Pool Glassfish v3

    - by jon
    Hi all, I am experiencing problems creating a connection pool in glassfish v3, just for reference i am using the Java EE glassfish bundle. my enviroment vars are as follows Url: jdbc:oracle:thin:@localhost:1521:xe User: sys Password : xxxxxxxx which i think is all i need to make a connection. but i get the following exception WARNING: Can not find resource bundle for this logger. class name that failed: com.sun.gjc.common.DataSourceObjectBuilder SEVERE: jdbc.exc_cnfe_ds java.lang.ClassNotFoundException: oracle.jdbc.pool.OracleDataSource at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:248) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:247) at com.sun.gjc.common.DataSourceObjectBuilder.getDataSourceObject(DataSourceObjectBuilder.java:279) at com.sun.gjc.common.DataSourceObjectBuilder.constructDataSourceObject(DataSourceObjectBuilder.java:108) at com.sun.gjc.spi.ManagedConnectionFactory.getDataSource(ManagedConnectionFactory.java:1167) at com.sun.gjc.spi.DSManagedConnectionFactory.getDataSource(DSManagedConnectionFactory.java:135) at com.sun.gjc.spi.DSManagedConnectionFactory.createManagedConnection(DSManagedConnectionFactory.java:90) at com.sun.enterprise.connectors.service.ConnectorConnectionPoolAdminServiceImpl.getManagedConnection(ConnectorConnectionPoolAdminServiceImpl.java:520) at com.sun.enterprise.connectors.service.ConnectorConnectionPoolAdminServiceImpl.getUnpooledConnection(ConnectorConnectionPoolAdminServiceImpl.java:630) at com.sun.enterprise.connectors.service.ConnectorConnectionPoolAdminServiceImpl.testConnectionPool(ConnectorConnectionPoolAdminServiceImpl.java:442) at com.sun.enterprise.connectors.ConnectorRuntime.pingConnectionPool(ConnectorRuntime.java:898) at org.glassfish.admin.amx.impl.ext.ConnectorRuntimeAPIProviderImpl.pingJDBCConnectionPool(ConnectorRuntimeAPIProviderImpl.java:570) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.glassfish.admin.amx.impl.mbean.AMXImplBase.invoke(AMXImplBase.java:1038) at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:836) at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:761) at javax.management.MBeanServerInvocationHandler.invoke(MBeanServerInvocationHandler.java:288) at org.glassfish.admin.amx.util.jmx.MBeanProxyHandler.invoke(MBeanProxyHandler.java:453) at org.glassfish.admin.amx.core.proxy.AMXProxyHandler._invoke(AMXProxyHandler.java:822) at org.glassfish.admin.amx.core.proxy.AMXProxyHandler.invoke(AMXProxyHandler.java:526) at $Proxy233.pingJDBCConnectionPool(Unknown Source) at org.glassfish.admingui.common.handlers.JdbcTempHandler.pingJdbcConnectionPool(JdbcTempHandler.java:99) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.sun.jsftemplating.layout.descriptors.handler.Handler.invoke(Handler.java:442) at com.sun.jsftemplating.layout.descriptors.LayoutElementBase.dispatchHandlers(LayoutElementBase.java:420) at com.sun.jsftemplating.layout.descriptors.LayoutElementBase.dispatchHandlers(LayoutElementBase.java:394) at com.sun.jsftemplating.layout.event.CommandActionListener.invokeCommandHandlers(CommandActionListener.java:150) at com.sun.jsftemplating.layout.event.CommandActionListener.processAction(CommandActionListener.java:98) at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88) at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:772) at javax.faces.component.UICommand.broadcast(UICommand.java:300) at com.sun.webui.jsf.component.WebuiCommand.broadcast(WebuiCommand.java:160) at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775) at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267) at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:312) at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:215) at com.sun.webui.jsf.util.UploadFilter.doFilter(UploadFilter.java:240) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:215) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:277) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641) at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97) at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185) at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:332) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:233) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:239) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57) at com.sun.grizzly.ContextTask.run(ContextTask.java:69) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309) at java.lang.Thread.run(Thread.java:619) WARNING: RAR8054: Exception while creating an unpooled [test] connection for pool [ testingManagmentDataConnection ], Class name is wrong or classpath is not set for : oracle.jdbc.pool.OracleDataSource WARNING: Can not find resource bundle for this logger. class name that failed: com.sun.gjc.common.DataSourceObjectBuilder does anyone have any ideas what i am doing wrong/ what i will have to do to correct this issue, Thanks for your time Jon

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  • multiple-inheritance substitution

    - by Luigi
    I want to write a module (framework specific), that would wrap and extend Facebook PHP-sdk (https://github.com/facebook/php-sdk/). My problem is - how to organize classes, in a nice way. So getting into details - Facebook PHP-sdk consists of two classes: BaseFacebook - abstract class with all the stuff sdk does Facebook - extends BaseFacebook, and implements parent abstract persistance-related methods with default session usage Now I have some functionality to add: Facebook class substitution, integrated with framework session class shorthand methods, that run api calls, I use mostly (through BaseFacebook::api()), authorization methods, so i don't have to rewrite this logic every time, configuration, sucked up from framework classes, insted of passed as params caching, integrated with framework cache module I know something has gone very wrong, because I have too much inheritance that doesn't look very normal.Wrapping everything in one "complex extension" class also seems too much. I think I should have few working togheter classes - but i get into problems like: if cache class doesn't really extend and override BaseFacebook::api() method - shorthand and authentication classes won't be able to use the caching. Maybe some kind of a pattern would be right in here? How would you organize these classes and their dependencies? EDIT 04.07.2012 Bits of code, related to the topic: This is how the base class of Facebook PHP-sdk: abstract class BaseFacebook { // ... some methods public function api(/* polymorphic */) { // ... method, that makes api calls } public function getUser() { // ... tries to get user id from session } // ... other methods abstract protected function setPersistentData($key, $value); abstract protected function getPersistentData($key, $default = false); // ... few more abstract methods } Normaly Facebook class extends it, and impelements those abstract methods. I replaced it with my substitude - Facebook_Session class: class Facebook_Session extends BaseFacebook { protected function setPersistentData($key, $value) { // ... method body } protected function getPersistentData($key, $default = false) { // ... method body } // ... implementation of other abstract functions from BaseFacebook } Ok, then I extend this more with shorthand methods and configuration variables: class Facebook_Custom extends Facebook_Session { public funtion __construct() { // ... call parent's constructor with parameters from framework config } public function api_batch() { // ... a wrapper for parent's api() method return $this->api('/?batch=' . json_encode($calls), 'POST'); } public function redirect_to_auth_dialog() { // method body } // ... more methods like this, for common queries / authorization } I'm not sure, if this isn't too much for a single class ( authorization / shorthand methods / configuration). Then there comes another extending layer - cache: class Facebook_Cache extends Facebook_Custom { public function api() { $cache_file_identifier = $this->getUser(); if(/* cache_file_identifier is not null and found a valid file with cached query result */) { // return the result } else { try { // call Facebook_Custom::api, cache and return the result } catch(FacebookApiException $e) { // if Access Token is expired force refreshing it parent::redirect_to_auth_dialog(); } } } // .. some other stuff related to caching } Now this pretty much works. New instance of Facebook_Cache gives me all the functionality. Shorthand methods from Facebook_Custom use caching, because Facebook_Cache overwrited api() method. But here is what is bothering me: I think it's too much inheritance. It's all very tight coupled - like look how i had to specify 'Facebook_Custom::api' instead of 'parent:api', to avoid api() method loop on Facebook_Cache class extending. Overall mess and ugliness. So again, this works but I'm just asking about patterns / ways of doing this in a cleaner and smarter way.

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  • .NET Declarative Security: Why is SecurityAction.Deny impossible to work with?

    - by rally25rs
    I've been messing with this for about a day and a half now sifting through .NET reflector and MSDN docs, and can't figure anything out... As it stands in the .NET framework, you can demand that the current Principal belong to a role to be able to execute a method by marking a method like this: [PrincipalPermission(SecurityAction.Demand, Role = "CanEdit")] public void Save() { ... } I am working with an existing security model that already has a "ReadOnly" role defined, so I need to do exactly the opposite of above... block the Save() method if a user is in the "ReadOnly" role. No problem, right? just flip the SecurityAction to .Deny: [PrincipalPermission(SecurityAction.Deny, Role = "ReadOnly")] public void Save() { ... } Well, it turns out that this does nothing at all. The method still runs fine. It seems that the PrincipalPermissionAttribute defines: public override IPermission CreatePermission() But when the attribute is set to SecurityAction.Deny, this method is never called, so no IPermission object is ever created. Does anyone know of a way to get .Deny to work? I've been trying to make a custom secutiry attribute, but even that doesn't work. I tried to get tricky and do: public class MyPermissionAttribute : CodeAccessSecurityAttribute { private SecurityAction securityAction; public MyPermissionAttribute(SecurityAction action) : base(SecurityAction.Demand) { if (action != SecurityAction.Demand && action != SecurityAction.Deny) throw new ArgumentException("Unsupported SecurityAction. Only Demand and Deny are supported."); this.securityAction = action; } public override IPermission CreatePermission() { // do something based on the SecurityAction... } } Notice my attribute constructor always passes SecurityAction.Demand, which is the one action that would work previously. However, even in this case, the CreatePermission() method is still only called when the attribute is set to .Demand, and not .Deny! Maybe the runtime is actually checking the attribute instead of the SecurityAction passed to the CodeAccessSecurityAttribute constructor? I'm not sure what else to try here... anyone have any ideas? You wouldn't think it would be that hard to deny method access based on a role, instead of only demanding it. It really disturbed me that the default PrincipalPermission appears from within an IDE like it would be just fine doing a .Deny, and there is like a 1-liner in the MSDN docs that hint that it won't work. You would think the PrincipalPermissionAttribute constructor would throw an exception immediately if anything other that .Demand is specified, since that could create a big security hole! I never would have realized that .Deny does nothing at all if I hadn't been unit testing! Again, all this stems from having to deal with an existing security model that has a "ReadOnly" role that needs to be denied access, instead of doing it the other way around, where I cna just grant access to a role. Thanks for any help! Quick followup: I can actually make my custom attribute work by doing this: public class MyPermissionAttribute : CodeAccessSecurityAttribute { public SecurityAction SecurityAction { get; set; } public MyPermissionAttribute(SecurityAction action) : base(action) { } public override IPermission CreatePermission() { switch(this.SecurityAction) { ... } // check Demand or Deny } } And decorating the method: [MyPermission(SecurityAction.Demand, SecurityAction = SecurityAction.Deny, Role = "ReadOnly")] public void Save() { ... } But that is terribly ugly, since I'm specifying both Demand and Deny in the same attribute. But it does work... Another interesting note: My custom class extends CodeAccessSecurityAttribute, which in turn only extends SecurityAttribute. If I cnage my custom class to directly extend SecurityAttribute, then nothing at all works. So it seems the runtime is definately looking for only CodeAccessSecurityAttribute instances in the metadata, and does something funny with the SecurityAction specified, even if a custom constructor overrides it.

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  • JSF SSL Hazzard

    - by java beginner
    In my application it is required that only certain pages need to be secured using SSL so I configured it security-constraint> <display-name>Security Settings</display-name> <web-resource-collection> <web-resource-name>SSL Pages</web-resource-name> <description/> <url-pattern>/*.jsp</url-pattern> <http-method>GET</http-method> <http-method>POST</http-method> </web-resource-collection> <user-data-constraint> <description>CONFIDENTIAL requires SSL</description> <transport-guarantee>CONFIDENTIAL</transport-guarantee> </user-data-constraint> and added filter http://blogs.sun.com/jluehe/entry/how_to_downshift_from_https but only one hazard is there. I am using it with richFaces. Once it goes to HTTPS its not changing the page—I mean if I perform post action it doesn't actually happen. But if I do it from the local machine's browser it works perfectly, from a remote browser it stucks with HTTPS and not changing after that. Here is my web.xml's snap: <filter> <filter-name>MyFilter</filter-name> <filter-class>MyFilter</filter-class> <init-param> <param-name>httpPort</param-name> <param-value>8080</param-value> </init-param> </filter> <filter-mapping> <filter-name>MyFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <security-constraint> <web-resource-collection> <web-resource-name>Protected resource</web-resource-name> <url-pattern>somePattern</url-pattern> <http-method>GET</http-method> <http-method>POST</http-method> </web-resource-collection> <user-data-constraint> <transport-guarantee>CONFIDENTIAL</transport-guarantee> </user-data-constraint> </security-constraint> and some other filters of richfaces. Problem is strange. If I try to access the web app from local's machine's browser it works fine but in remote machine's browser once it get into HTTP, all the forms of that page aswell as href stops working.(JSF,facelet is used.)

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  • How to determine if two generic type values are equal?

    - by comecme
    I'm trying to figure out how I can successfully determine if two generic type values are equal to each other. Based on Mark Byers' answer on this question I would think I can just use value.Equals() where value is a generic type. My actual problem is in a LinkedList implementation, but the problem can be shown with this simpler example. class GenericOjbect<T> { public T Value { get; private set; } public GenericOjbect(T value) { Value = value; } public bool Equals(T value) { return (Value.Equals(value)); } } Now I define an instance of GenericObject<StringBuilder> containing new StringBuilder("StackOverflow"). I would expect to get true if I call Equals(new StringBuilder("StackOverflow") on this GenericObject instance, but I get false. A sample program showing this: using System; using System.Text; class Program { static void Main() { var sb1 = new StringBuilder("StackOverflow"); var sb2 = new StringBuilder("StackOverflow"); Console.WriteLine("StringBuilder compare"); Console.WriteLine("1. == " + (sb1 == sb2)); Console.WriteLine("2. Object.Equals " + (Object.Equals(sb1, sb2))); Console.WriteLine("3. this.Equals " + (sb1.Equals(sb2))); var go1 = new GenericOjbect<StringBuilder>(sb1); var go2 = new GenericOjbect<StringBuilder>(sb2); Console.WriteLine("\nGenericObject compare"); Console.WriteLine("1. == " + (go1 == go2)); Console.WriteLine("2. Object.Equals " + (Object.Equals(go1, go2))); Console.WriteLine("3. this.Equals " + (go1.Equals(go2))); Console.WriteLine("4. Value.Equals " + (go1.Value.Equals(go2.Value))); } } For the three methods of comparing two StringBuilder objects, only the StringBuilder.Equals instance method (the third line) returns true. This is what I expected. But when comparing the GenericObject objects, its Equals() method (the third line) returns false. Interestingly enough, the fourth compare method does return true. I'd think the third and fourth comparison are actually doing the same thing. I would have expected true. Because in the Equals() method of the GenericObject class, both value and Value are of type T which in this case is a StringBuilder. Based on Mark Byers' answer in this question, I would've expected the Value.Equals() method to be using the StringBuilder's Equals() method. And as I've shown, the StringBuilder's Equal() method does return true. I've even tried public bool Equals(T value) { return EqualityComparer<T>.Default.Equals(Value, value); } but that also returns false. So, two questions here: Why doesn't the code return true? How could I implement the Equals method so it does return true?

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  • Partial generic type inference possible in C#?

    - by Lasse V. Karlsen
    I am working on rewriting my fluent interface for my IoC class library, and when I refactored some code in order to share some common functionality through a base class, I hit upon a snag. Note: This is something I want to do, not something I have to do. If I have to make do with a different syntax, I will, but if anyone has an idea on how to make my code compile the way I want it, it would be most welcome. I want some extension methods to be available for a specific base-class, and these methods should be generic, with one generic type, related to an argument to the method, but the methods should also return a specific type related to the particular descendant they're invoked upon. Better with a code example than the above description methinks. Here's a simple and complete example of what doesn't work: using System; namespace ConsoleApplication16 { public class ParameterizedRegistrationBase { } public class ConcreteTypeRegistration : ParameterizedRegistrationBase { public void SomethingConcrete() { } } public class DelegateRegistration : ParameterizedRegistrationBase { public void SomethingDelegated() { } } public static class Extensions { public static ParameterizedRegistrationBase Parameter<T>( this ParameterizedRegistrationBase p, string name, T value) { return p; } } class Program { static void Main(string[] args) { ConcreteTypeRegistration ct = new ConcreteTypeRegistration(); ct .Parameter<int>("age", 20) .SomethingConcrete(); // <-- this is not available DelegateRegistration del = new DelegateRegistration(); del .Parameter<int>("age", 20) .SomethingDelegated(); // <-- neither is this } } } If you compile this, you'll get: 'ConsoleApplication16.ParameterizedRegistrationBase' does not contain a definition for 'SomethingConcrete' and no extension method 'SomethingConcrete'... 'ConsoleApplication16.ParameterizedRegistrationBase' does not contain a definition for 'SomethingDelegated' and no extension method 'SomethingDelegated'... What I want is for the extension method (Parameter<T>) to be able to be invoked on both ConcreteTypeRegistration and DelegateRegistration, and in both cases the return type should match the type the extension was invoked on. The problem is as follows: I would like to write: ct.Parameter<string>("name", "Lasse") ^------^ notice only one generic argument but also that Parameter<T> returns an object of the same type it was invoked on, which means: ct.Parameter<string>("name", "Lasse").SomethingConcrete(); ^ ^-------+-------^ | | +---------------------------------------------+ .SomethingConcrete comes from the object in "ct" which in this case is of type ConcreteTypeRegistration Is there any way I can trick the compiler into making this leap for me? If I add two generic type arguments to the Parameter method, type inference forces me to either provide both, or none, which means this: public static TReg Parameter<TReg, T>( this TReg p, string name, T value) where TReg : ParameterizedRegistrationBase gives me this: Using the generic method 'ConsoleApplication16.Extensions.Parameter<TReg,T>(TReg, string, T)' requires 2 type arguments Using the generic method 'ConsoleApplication16.Extensions.Parameter<TReg,T>(TReg, string, T)' requires 2 type arguments Which is just as bad. I can easily restructure the classes, or even make the methods non-extension-methods by introducing them into the hierarchy, but my question is if I can avoid having to duplicate the methods for the two descendants, and in some way declare them only once, for the base class. Let me rephrase that. Is there a way to change the classes in the first code example above, so that the syntax in the Main-method can be kept, without duplicating the methods in question? The code will have to be compatible with both C# 3.0 and 4.0. Edit: The reason I'd rather not leave both generic type arguments to inference is that for some services, I want to specify a parameter value for a constructor parameter that is of one type, but pass in a value that is a descendant. For the moment, matching of specified argument values and the correct constructor to call is done using both the name and the type of the argument. Let me give an example: ServiceContainerBuilder.Register<ISomeService>(r => r .From(f => f.ConcreteType<FileService>(ct => ct .Parameter<Stream>("source", new FileStream(...))))); ^--+---^ ^---+----^ | | | +- has to be a descendant of Stream | +- has to match constructor of FileService If I leave both to type inference, the parameter type will be FileStream, not Stream.

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  • Android passing an arraylist back to parent activity

    - by Nicklas O
    Hi there. I've been searching for a simple example of this with no luck. In my android application I have two activities: 1. The main activity which is launched at startup 2. A second activity which is launched by pressing a button on the main activty. When the second activity is finished (by pressing a button) I want it to send back an ArrayList of type MyObject to the main activity and close itself, which the main activity can then do whatever with it. How would I go about achieving this? I have been trying a few things but it is crashing my application when I start the second activity. When the user presses button to launch second activity: Intent i = new Intent(MainActivity.this, secondactivity.class); startActivityForResult(i, 1); The array which is bundled back after pressing a button on the second activity: Intent intent= getIntent(); Bundle b = new Bundle(); b.putParcelableArrayList("myarraylist", mylist); intent.putExtras(b); setResult(RESULT_OK, intent); finish(); And finally a listener on the main activity (although I'm not sure of 100% when this code launches...) protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); if(resultCode==RESULT_OK && requestCode==1){ Bundle extras = data.getExtras(); final ArrayList<MyObject> mylist = extras.getParcelableArrayList("myarraylist"); Toast.makeText(MainActivity.this, mylist.get(0).getName(), Toast.LENGTH_SHORT).show(); } } Any ideas where I am going wrong? The onActivityResult() seems to be crashing my application. EDIT: This is my class MyObject, its called plan and has a name and an id import android.os.Parcel; import android.os.Parcelable; public class Plan implements Parcelable{ private String name; private String id; public Plan(){ } public Plan(String name, String id){ this.name = name; this.id = id; } public String getName(){ return name; } public void setName(String name){ this.name = name; } public String getId(){ return id; } public void setId(String id){ this.id = id; } public String toString(){ return "Plan ID: " + id + " Plan Name: " + name; } @Override public int describeContents() { // TODO Auto-generated method stub return 0; } @Override public void writeToParcel(Parcel dest, int flags) { dest.writeString(id); dest.writeString(name); } public static final Parcelable.Creator<Plan> CREATOR = new Parcelable.Creator<Plan>() { public Plan createFromParcel(Parcel in) { return new Plan(); } @Override public Plan[] newArray(int size) { // TODO Auto-generated method stub return new Plan[size]; } }; } This is my logcat E/AndroidRuntime( 293): java.lang.RuntimeException: Unable to instantiate activ ity ComponentInfo{com.daniel.android.groupproject/com.me.android.projec t.secondactivity}: java.lang.NullPointerException E/AndroidRuntime( 293): at android.app.ActivityThread.performLaunchActiv ity(ActivityThread.java:2417) E/AndroidRuntime( 293): at android.app.ActivityThread.handleLaunchActivi ty(ActivityThread.java:2512) E/AndroidRuntime( 293): at android.app.ActivityThread.access$2200(Activi tyThread.java:119) E/AndroidRuntime( 293): at android.app.ActivityThread$H.handleMessage(Ac tivityThread.java:1863) E/AndroidRuntime( 293): at android.os.Handler.dispatchMessage(Handler.ja va:99) E/AndroidRuntime( 293): at android.os.Looper.loop(Looper.java:123) E/AndroidRuntime( 293): at android.app.ActivityThread.main(ActivityThrea d.java:4363) E/AndroidRuntime( 293): at java.lang.reflect.Method.invokeNative(Native Method) E/AndroidRuntime( 293): at java.lang.reflect.Method.invoke(Method.java:5 21) E/AndroidRuntime( 293): at com.android.internal.os.ZygoteInit$MethodAndA rgsCaller.run(ZygoteInit.java:860) E/AndroidRuntime( 293): at com.android.internal.os.ZygoteInit.main(Zygot eInit.java:618) E/AndroidRuntime( 293): at dalvik.system.NativeStart.main(Native Method) E/AndroidRuntime( 293): Caused by: java.lang.NullPointerException E/AndroidRuntime( 293): at com.daniel.android.groupproject.login.<init>( login.java:51) E/AndroidRuntime( 293): at java.lang.Class.newInstanceImpl(Native Method ) E/AndroidRuntime( 293): at java.lang.Class.newInstance(Class.java:1479) E/AndroidRuntime( 293): at android.app.Instrumentation.newActivity(Instr umentation.java:1021) E/AndroidRuntime( 293): at android.app.ActivityThread.performLaunchActiv ity(ActivityThread.java:2409) E/AndroidRuntime( 293): ... 11 more

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  • Is this a reasonable way to handle getters/setters in a PHP class?

    - by Mark Biek
    I'm going to try something with the format of this question and I'm very open to suggestions about a better way to handle it. I didn't want to just dump a bunch of code in the question so I've posted the code for the class on refactormycode. base-class-for-easy-class-property-handling My thought was that people can either post code snippets here or make changes on refactormycode and post links back to their refactorings. I'll make upvotes and accept an answer (assuming there's a clear "winner") based on that. At any rate, on to the class itself: I see a lot of debate about getter/setter class methods and is it better to just access simple property variables directly or should every class have explicit get/set methods defined, blah blah blah. I like the idea of having explicit methods in case you have to add more logic later. Then you don't have to modify any code that uses the class. However I hate having a million functions that look like this: public function getFirstName() { return $this->firstName; } public function setFirstName($firstName) { return $this->firstName; } Now I'm sure I'm not the first person to do this (I'm hoping that there's a better way of doing it that someone can suggest to me). Basically, the PropertyHandler class has a __call magic method. Any methods that come through __call that start with "get" or "set" are then routed to functions that set or retrieve values into an associative array. The key into the array is the name of the calling method after get or set. So, if the method coming into __call is "getFirstName", the array key is "FirstName". I liked using __call because it will automatically take care of the case where the subclass already has a "getFirstName" method defined. My impression (and I may be wrong) is that the __get & __set magic methods don't do that. So here's an example of how it would work: class PropTest extends PropertyHandler { public function __construct() { parent::__construct(); } } $props = new PropTest(); $props->setFirstName("Mark"); echo $props->getFirstName(); Notice that PropTest doesn't actually have "setFirstName" or "getFirstName" methods and neither does PropertyHandler. All that's doing is manipulating array values. The other case would be where your subclass is already extending something else. Since you can't have true multiple inheritance in PHP, you can make your subclass have a PropertyHandler instance as a private variable. You have to add one more function but then things behave in exactly the same way. class PropTest2 { private $props; public function __construct() { $this->props = new PropertyHandler(); } public function __call($method, $arguments) { return $this->props->__call($method, $arguments); } } $props2 = new PropTest2(); $props2->setFirstName('Mark'); echo $props2->getFirstName(); Notice how the subclass has a __call method that just passes everything along to the PropertyHandler __call method. Another good argument against handling getters and setters this way is that it makes it really hard to document. In fact, it's basically impossible to use any sort of document generation tool since the explicit methods to be don't documented don't exist. I've pretty much abandoned this approach for now. It was an interesting learning exercise but I think it sacrifices too much clarity.

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  • ASP.NET MVC 3 - New Features

    - by imran_ku07
    Introduction:          ASP.NET MVC 3 just released by ASP.NET MVC team which includes some new features, some changes, some improvements and bug fixes. In this article, I will show you the new features of ASP.NET MVC 3. This will help you to get started using the new features of ASP.NET MVC 3. Full details of this announcement is available at Announcing release of ASP.NET MVC 3, IIS Express, SQL CE 4, Web Farm Framework, Orchard, WebMatrix.   Description:       New Razor View Engine:              Razor view engine is one of the most coolest new feature in ASP.NET MVC 3. Razor is speeding things up just a little bit more. It is much smaller and lighter in size. Also it is very easy to learn. You can say ' write less, do more '. You can get start and learn more about Razor at Introducing “Razor” – a new view engine for ASP.NET.         Granular Request Validation:             Another biggest new feature in ASP.NET MVC 3 is Granular Request Validation. Default request validator will throw an exception when he see < followed by an exclamation(like <!) or < followed by the letters a through z(like <s) or & followed by a pound sign(like &#123) as a part of querystring, posted form, headers and cookie collection. In previous versions of ASP.NET MVC, you can control request validation using ValidateInputAttriubte. In ASP.NET MVC 3 you can control request validation at Model level by annotating your model properties with a new attribute called AllowHtmlAttribute. For details see Granular Request Validation in ASP.NET MVC 3.       Sessionless Controller Support:             Sessionless Controller is another great new feature in ASP.NET MVC 3. With Sessionless Controller you can easily control your session behavior for controllers. For example, you can make your HomeController's Session as Disabled or ReadOnly, allowing concurrent request execution for single user. For details see Concurrent Requests In ASP.NET MVC and HowTo: Sessionless Controller in MVC3 – what & and why?.       Unobtrusive Ajax and  Unobtrusive Client Side Validation is Supported:             Another cool new feature in ASP.NET MVC 3 is support for Unobtrusive Ajax and Unobtrusive Client Side Validation.  This feature allows separation of responsibilities within your web application by separating your html with your script. For details see Unobtrusive Ajax in ASP.NET MVC 3 and Unobtrusive Client Validation in ASP.NET MVC 3.       Dependency Resolver:             Dependency Resolver is another great feature of ASP.NET MVC 3. It allows you to register a dependency resolver that will be used by the framework. With this approach your application will not become tightly coupled and the dependency will be injected at run time. For details see ASP.NET MVC 3 Service Location.       New Helper Methods:             ASP.NET MVC 3 includes some helper methods of ASP.NET Web Pages technology that are used for common functionality. These helper methods includes: Chart, Crypto, WebGrid, WebImage and WebMail. For details of these helper methods, please see ASP.NET MVC 3 Release Notes. For using other helper methods of ASP.NET Web Pages see Using ASP.NET Web Pages Helpers in ASP.NET MVC.       Child Action Output Caching:             ASP.NET MVC 3 also includes another feature called Child Action Output Caching. This allows you to cache only a portion of the response when you are using Html.RenderAction or Html.Action. This cache can be varied by action name, action method signature and action method parameter values. For details see this.       RemoteAttribute:             ASP.NET MVC 3 allows you to validate a form field by making a remote server call through Ajax. This makes it very easy to perform remote validation at client side and quickly give the feedback to the user. For details see How to: Implement Remote Validation in ASP.NET MVC.       CompareAttribute:             ASP.NET MVC 3 includes a new validation attribute called CompareAttribute. CompareAttribute allows you to compare the values of two different properties of a model. For details see CompareAttribute in ASP.NET MVC 3.       Miscellaneous New Features:                    ASP.NET MVC 2 includes FormValueProvider, QueryStringValueProvider, RouteDataValueProvider and HttpFileCollectionValueProvider. ASP.NET MVC 3 adds two additional value providers, ChildActionValueProvider and JsonValueProvider(JsonValueProvider is not physically exist).  ChildActionValueProvider is used when you issue a child request using Html.Action and/or Html.RenderAction methods, so that your explicit parameter values in Html.Action and/or Html.RenderAction will always take precedence over other value providers. JsonValueProvider is used to model bind JSON data. For details see Sending JSON to an ASP.NET MVC Action Method Argument.           In ASP.NET MVC 3, a new property named FileExtensions added to the VirtualPathProviderViewEngine class. This property is used when looking up a view by path (and not by name), so that only views with a file extension contained in the list specified by this new property is considered. For details see VirtualPathProviderViewEngine.FileExtensions Property .           ASP.NET MVC 3 installation package also includes the NuGet Package Manager which will be automatically installed when you install ASP.NET MVC 3. NuGet makes it easy to install and update open source libraries and tools in Visual Studio. See this for details.           In ASP.NET MVC 2, client side validation will not trigger for overridden model properties. For example, if have you a Model that contains some overridden properties then client side validation will not trigger for overridden properties in ASP.NET MVC 2 but client side validation will work for overridden properties in ASP.NET MVC 3.           Client side validation is not supported for StringLengthAttribute.MinimumLength property in ASP.NET MVC 2. In ASP.NET MVC 3 client side validation will work for StringLengthAttribute.MinimumLength property.           ASP.NET MVC 3 includes new action results like HttpUnauthorizedResult, HttpNotFoundResult and HttpStatusCodeResult.           ASP.NET MVC 3 includes some new overloads of LabelFor and LabelForModel methods. For details see LabelExtensions.LabelForModel and LabelExtensions.LabelFor.           In ASP.NET MVC 3, IControllerFactory includes a new method GetControllerSessionBehavior. This method is used to get controller's session behavior. For details see IControllerFactory.GetControllerSessionBehavior Method.           In ASP.NET MVC 3, Controller class includes a new property ViewBag which is of type dynamic. This property allows you to access ViewData Dictionary using C # 4.0 dynamic features. For details see ControllerBase.ViewBag Property.           ModelMetadata includes a property AdditionalValues which is of type Dictionary. In ASP.NET MVC 3 you can populate this property using AdditionalMetadataAttribute. For details see AdditionalMetadataAttribute Class.           In ASP.NET MVC 3 you can also use MvcScaffolding to scaffold your Views and Controller. For details see Scaffold your ASP.NET MVC 3 project with the MvcScaffolding package.           If you want to convert your application from ASP.NET MVC 2 to ASP.NET MVC 3 then there is an excellent tool that automatically converts ASP.NET MVC 2 application to ASP.NET MVC 3 application. For details see MVC 3 Project Upgrade Tool.           In ASP.NET MVC 2 DisplayAttribute is not supported but in ASP.NET MVC 3 DisplayAttribute will work properly.           ASP.NET MVC 3 also support model level validation via the new IValidatableObject interface.           ASP.NET MVC 3 includes a new helper method Html.Raw. This helper method allows you to display unencoded HTML.     Summary:          In this article I showed you the new features of ASP.NET MVC 3. This will help you a lot when you start using ASP MVC 3. I also provide you the links where you can find further details. Hopefully you will enjoy this article too.  

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  • Netflix, jQuery, JSONP, and OData

    - by Stephen Walther
    At the last MIX conference, Netflix announced that they are exposing their catalog of movie information using the OData protocol. This is great news! This means that you can take advantage of all of the advanced OData querying features against a live database of Netflix movies. In this blog entry, I’ll demonstrate how you can use Netflix, jQuery, JSONP, and OData to create a simple movie lookup form. The form enables you to enter a movie title, or part of a movie title, and display a list of matching movies. For example, Figure 1 illustrates the movies displayed when you enter the value robot into the lookup form.   Using the Netflix OData Catalog API You can learn about the Netflix OData Catalog API at the following website: http://developer.netflix.com/docs/oData_Catalog The nice thing about this website is that it provides plenty of samples. It also has a good general reference for OData. For example, the website includes a list of OData filter operators and functions. The Netflix Catalog API exposes 4 top-level resources: Titles – A database of Movie information including interesting movie properties such as synopsis, BoxArt, and Cast. People – A database of people information including interesting information such as Awards, TitlesDirected, and TitlesActedIn. Languages – Enables you to get title information in different languages. Genres – Enables you to get title information for specific movie genres. OData is REST based. This means that you can perform queries by putting together the right URL. For example, if you want to get a list of the movies that were released after 2010 and that had an average rating greater than 4 then you can enter the following URL in the address bar of your browser: http://odata.netflix.com/Catalog/Titles?$filter=ReleaseYear gt 2010&AverageRating gt 4 Entering this URL returns the movies in Figure 2. Creating the Movie Lookup Form The complete code for the Movie Lookup form is contained in Listing 1. Listing 1 – MovieLookup.htm <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Netflix with jQuery</title> <style type="text/css"> #movieTemplateContainer div { width:400px; padding: 10px; margin: 10px; border: black solid 1px; } </style> <script src="http://ajax.microsoft.com/ajax/jquery/jquery-1.4.2.js" type="text/javascript"></script> <script src="App_Scripts/Microtemplates.js" type="text/javascript"></script> </head> <body> <label>Search Movies:</label> <input id="movieName" size="50" /> <button id="btnLookup">Lookup</button> <div id="movieTemplateContainer"></div> <script id="movieTemplate" type="text/html"> <div> <img src="<%=BoxArtSmallUrl %>" /> <strong><%=Name%></strong> <p> <%=Synopsis %> </p> </div> </script> <script type="text/javascript"> $("#btnLookup").click(function () { // Build OData query var movieName = $("#movieName").val(); var query = "http://odata.netflix.com/Catalog" // netflix base url + "/Titles" // top-level resource + "?$filter=substringof('" + escape(movieName) + "',Name)" // filter by movie name + "&$callback=callback" // jsonp request + "&$format=json"; // json request // Make JSONP call to Netflix $.ajax({ dataType: "jsonp", url: query, jsonpCallback: "callback", success: callback }); }); function callback(result) { // unwrap result var movies = result["d"]["results"]; // show movies in template var showMovie = tmpl("movieTemplate"); var html = ""; for (var i = 0; i < movies.length; i++) { // flatten movie movies[i].BoxArtSmallUrl = movies[i].BoxArt.SmallUrl; // render with template html += showMovie(movies[i]); } $("#movieTemplateContainer").html(html); } </script> </body> </html> The HTML page in Listing 1 includes two JavaScript libraries: <script src="http://ajax.microsoft.com/ajax/jquery/jquery-1.4.2.js" type="text/javascript"></script> <script src="App_Scripts/Microtemplates.js" type="text/javascript"></script> The first script tag retrieves jQuery from the Microsoft Ajax CDN. You can learn more about the Microsoft Ajax CDN by visiting the following website: http://www.asp.net/ajaxLibrary/cdn.ashx The second script tag is used to reference Resig’s micro-templating library. Because I want to use a template to display each movie, I need this library: http://ejohn.org/blog/javascript-micro-templating/ When you enter a value into the Search Movies input field and click the button, the following JavaScript code is executed: // Build OData query var movieName = $("#movieName").val(); var query = "http://odata.netflix.com/Catalog" // netflix base url + "/Titles" // top-level resource + "?$filter=substringof('" + escape(movieName) + "',Name)" // filter by movie name + "&$callback=callback" // jsonp request + "&$format=json"; // json request // Make JSONP call to Netflix $.ajax({ dataType: "jsonp", url: query, jsonpCallback: "callback", success: callback }); This code Is used to build a query that will be executed against the Netflix Catalog API. For example, if you enter the search phrase King Kong then the following URL is created: http://odata.netflix.com/Catalog/Titles?$filter=substringof(‘King%20Kong’,Name)&$callback=callback&$format=json This query includes the following parameters: $filter – You assign a filter expression to this parameter to filter the movie results. $callback – You assign the name of a JavaScript callback method to this parameter. OData calls this method to return the movie results. $format – you assign either the value json or xml to this parameter to specify how the format of the movie results. Notice that all of the OData parameters -- $filter, $callback, $format -- start with a dollar sign $. The Movie Lookup form uses JSONP to retrieve data across the Internet. Because WCF Data Services supports JSONP, and Netflix uses WCF Data Services to expose movies using the OData protocol, you can use JSONP when interacting with the Netflix Catalog API. To learn more about using JSONP with OData, see Pablo Castro’s blog: http://blogs.msdn.com/pablo/archive/2009/02/25/adding-support-for-jsonp-and-url-controlled-format-to-ado-net-data-services.aspx The actual JSONP call is performed by calling the $.ajax() method. When this call successfully completes, the JavaScript callback() method is called. The callback() method looks like this: function callback(result) { // unwrap result var movies = result["d"]["results"]; // show movies in template var showMovie = tmpl("movieTemplate"); var html = ""; for (var i = 0; i < movies.length; i++) { // flatten movie movies[i].BoxArtSmallUrl = movies[i].BoxArt.SmallUrl; // render with template html += showMovie(movies[i]); } $("#movieTemplateContainer").html(html); } The movie results from Netflix are passed to the callback method. The callback method takes advantage of Resig’s micro-templating library to display each of the movie results. A template used to display each movie is passed to the tmpl() method. The movie template looks like this: <script id="movieTemplate" type="text/html"> <div> <img src="<%=BoxArtSmallUrl %>" /> <strong><%=Name%></strong> <p> <%=Synopsis %> </p> </div> </script>   This template looks like a server-side ASP.NET template. However, the template is rendered in the client (browser) instead of the server. Summary The goal of this blog entry was to demonstrate how well jQuery works with OData. We managed to use a number of interesting open-source libraries and open protocols while building the Movie Lookup form including jQuery, JSONP, JSON, and OData.

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  • Using a WPF ListView as a DataGrid

    - by psheriff
    Many people like to view data in a grid format of rows and columns. WPF did not come with a data grid control that automatically creates rows and columns for you based on the object you pass it. However, the WPF Toolkit can be downloaded from CodePlex.com that does contain a DataGrid control. This DataGrid gives you the ability to pass it a DataTable or a Collection class and it will automatically figure out the columns or properties and create all the columns for you and display the data.The DataGrid control also supports editing and many other features that you might not always need. This means that the DataGrid does take a little more time to render the data. If you want to just display data (see Figure 1) in a grid format, then a ListView works quite well for this task. Of course, you will need to create the columns for the ListView, but with just a little generic code, you can create the columns on the fly just like the WPF Toolkit’s DataGrid. Figure 1: A List of Data using a ListView A Simple ListView ControlThe XAML below is what you would use to create the ListView shown in Figure 1. However, the problem with using XAML is you have to pre-define the columns. You cannot re-use this ListView except for “Product” data. <ListView x:Name="lstData"          ItemsSource="{Binding}">  <ListView.View>    <GridView>      <GridViewColumn Header="Product ID"                      Width="Auto"               DisplayMemberBinding="{Binding Path=ProductId}" />      <GridViewColumn Header="Product Name"                      Width="Auto"               DisplayMemberBinding="{Binding Path=ProductName}" />      <GridViewColumn Header="Price"                      Width="Auto"               DisplayMemberBinding="{Binding Path=Price}" />    </GridView>  </ListView.View></ListView> So, instead of creating the GridViewColumn’s in XAML, let’s learn to create them in code to create any amount of columns in a ListView. Create GridViewColumn’s From Data TableTo display multiple columns in a ListView control you need to set its View property to a GridView collection object. You add GridViewColumn objects to the GridView collection and assign the GridView to the View property. Each GridViewColumn object needs to be bound to a column or property name of the object that the ListView will be bound to. An ADO.NET DataTable object contains a collection of columns, and these columns have a ColumnName property which you use to bind to the GridViewColumn objects. Listing 1 shows a sample of reading and XML file into a DataSet object. After reading the data a GridView object is created. You can then loop through the DataTable columns collection and create a GridViewColumn object for each column in the DataTable. Notice the DisplayMemberBinding property is set to a new Binding to the ColumnName in the DataTable. C#private void FirstSample(){  // Read the data  DataSet ds = new DataSet();  ds.ReadXml(GetCurrentDirectory() + @"\Xml\Product.xml");    // Create the GridView  GridView gv = new GridView();   // Create the GridView Columns  foreach (DataColumn item in ds.Tables[0].Columns)  {    GridViewColumn gvc = new GridViewColumn();    gvc.DisplayMemberBinding = new Binding(item.ColumnName);    gvc.Header = item.ColumnName;    gvc.Width = Double.NaN;    gv.Columns.Add(gvc);  }   // Setup the GridView Columns  lstData.View = gv;  // Display the Data  lstData.DataContext = ds.Tables[0];} VB.NETPrivate Sub FirstSample()  ' Read the data  Dim ds As New DataSet()  ds.ReadXml(GetCurrentDirectory() & "\Xml\Product.xml")   ' Create the GridView  Dim gv As New GridView()   ' Create the GridView Columns  For Each item As DataColumn In ds.Tables(0).Columns    Dim gvc As New GridViewColumn()    gvc.DisplayMemberBinding = New Binding(item.ColumnName)    gvc.Header = item.ColumnName    gvc.Width = [Double].NaN    gv.Columns.Add(gvc)  Next   ' Setup the GridView Columns  lstData.View = gv  ' Display the Data  lstData.DataContext = ds.Tables(0)End SubListing 1: Loop through the DataTable columns collection to create GridViewColumn objects A Generic Method for Creating a GridViewInstead of having to write the code shown in Listing 1 for each ListView you wish to create, you can create a generic method that given any DataTable will return a GridView column collection. Listing 2 shows how you can simplify the code in Listing 1 by setting up a class called WPFListViewCommon and create a method called CreateGridViewColumns that returns your GridView. C#private void DataTableSample(){  // Read the data  DataSet ds = new DataSet();  ds.ReadXml(GetCurrentDirectory() + @"\Xml\Product.xml");   // Setup the GridView Columns  lstData.View =      WPFListViewCommon.CreateGridViewColumns(ds.Tables[0]);  lstData.DataContext = ds.Tables[0];} VB.NETPrivate Sub DataTableSample()  ' Read the data  Dim ds As New DataSet()  ds.ReadXml(GetCurrentDirectory() & "\Xml\Product.xml")   ' Setup the GridView Columns  lstData.View = _      WPFListViewCommon.CreateGridViewColumns(ds.Tables(0))  lstData.DataContext = ds.Tables(0)End SubListing 2: Call a generic method to create GridViewColumns. The CreateGridViewColumns MethodThe CreateGridViewColumns method will take a DataTable as a parameter and create a GridView object with a GridViewColumn object in its collection for each column in your DataTable. C#public static GridView CreateGridViewColumns(DataTable dt){  // Create the GridView  GridView gv = new GridView();  gv.AllowsColumnReorder = true;   // Create the GridView Columns  foreach (DataColumn item in dt.Columns)  {    GridViewColumn gvc = new GridViewColumn();    gvc.DisplayMemberBinding = new Binding(item.ColumnName);    gvc.Header = item.ColumnName;    gvc.Width = Double.NaN;    gv.Columns.Add(gvc);  }   return gv;} VB.NETPublic Shared Function CreateGridViewColumns _  (ByVal dt As DataTable) As GridView  ' Create the GridView  Dim gv As New GridView()  gv.AllowsColumnReorder = True   ' Create the GridView Columns  For Each item As DataColumn In dt.Columns    Dim gvc As New GridViewColumn()    gvc.DisplayMemberBinding = New Binding(item.ColumnName)    gvc.Header = item.ColumnName    gvc.Width = [Double].NaN    gv.Columns.Add(gvc)  Next   Return gvEnd FunctionListing 3: The CreateGridViewColumns method takes a DataTable and creates GridViewColumn objects in a GridView. By separating this method out into a class you can call this method anytime you want to create a ListView with a collection of columns from a DataTable. SummaryIn this blog you learned how to create a ListView that acts like a DataGrid. You are able to use a DataTable as both the source of the data, and for creating the columns for the ListView. In the next blog entry you will learn how to use the same technique, but for Collection classes. NOTE: You can download the complete sample code (in both VB and C#) at my website. http://www.pdsa.com/downloads. Choose Tips & Tricks, then "WPF ListView as a DataGrid" from the drop-down. Good Luck with your Coding,Paul Sheriff ** SPECIAL OFFER FOR MY BLOG READERS **Visit http://www.pdsa.com/Event/Blog for a free eBook on "Fundamentals of N-Tier".

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  • Parallelism in .NET – Part 7, Some Differences between PLINQ and LINQ to Objects

    - by Reed
    In my previous post on Declarative Data Parallelism, I mentioned that PLINQ extends LINQ to Objects to support parallel operations.  Although nearly all of the same operations are supported, there are some differences between PLINQ and LINQ to Objects.  By introducing Parallelism to our declarative model, we add some extra complexity.  This, in turn, adds some extra requirements that must be addressed. In order to illustrate the main differences, and why they exist, let’s begin by discussing some differences in how the two technologies operate, and look at the underlying types involved in LINQ to Objects and PLINQ . LINQ to Objects is mainly built upon a single class: Enumerable.  The Enumerable class is a static class that defines a large set of extension methods, nearly all of which work upon an IEnumerable<T>.  Many of these methods return a new IEnumerable<T>, allowing the methods to be chained together into a fluent style interface.  This is what allows us to write statements that chain together, and lead to the nice declarative programming model of LINQ: double min = collection .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Other LINQ variants work in a similar fashion.  For example, most data-oriented LINQ providers are built upon an implementation of IQueryable<T>, which allows the database provider to turn a LINQ statement into an underlying SQL query, to be performed directly on the remote database. PLINQ is similar, but instead of being built upon the Enumerable class, most of PLINQ is built upon a new static class: ParallelEnumerable.  When using PLINQ, you typically begin with any collection which implements IEnumerable<T>, and convert it to a new type using an extension method defined on ParallelEnumerable: AsParallel().  This method takes any IEnumerable<T>, and converts it into a ParallelQuery<T>, the core class for PLINQ.  There is a similar ParallelQuery class for working with non-generic IEnumerable implementations. This brings us to our first subtle, but important difference between PLINQ and LINQ – PLINQ always works upon specific types, which must be explicitly created. Typically, the type you’ll use with PLINQ is ParallelQuery<T>, but it can sometimes be a ParallelQuery or an OrderedParallelQuery<T>.  Instead of dealing with an interface, implemented by an unknown class, we’re dealing with a specific class type.  This works seamlessly from a usage standpoint – ParallelQuery<T> implements IEnumerable<T>, so you can always “switch back” to an IEnumerable<T>.  The difference only arises at the beginning of our parallelization.  When we’re using LINQ, and we want to process a normal collection via PLINQ, we need to explicitly convert the collection into a ParallelQuery<T> by calling AsParallel().  There is an important consideration here – AsParallel() does not need to be called on your specific collection, but rather any IEnumerable<T>.  This allows you to place it anywhere in the chain of methods involved in a LINQ statement, not just at the beginning.  This can be useful if you have an operation which will not parallelize well or is not thread safe.  For example, the following is perfectly valid, and similar to our previous examples: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); However, if SomeOperation() is not thread safe, we could just as easily do: double min = collection .Select(item => item.SomeOperation()) .AsParallel() .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); In this case, we’re using standard LINQ to Objects for the Select(…) method, then converting the results of that map routine to a ParallelQuery<T>, and processing our filter (the Where method) and our aggregation (the Min method) in parallel. PLINQ also provides us with a way to convert a ParallelQuery<T> back into a standard IEnumerable<T>, forcing sequential processing via standard LINQ to Objects.  If SomeOperation() was thread-safe, but PerformComputation() was not thread-safe, we would need to handle this by using the AsEnumerable() method: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .AsEnumerable() .Min(item => item.PerformComputation()); Here, we’re converting our collection into a ParallelQuery<T>, doing our map operation (the Select(…) method) and our filtering in parallel, then converting the collection back into a standard IEnumerable<T>, which causes our aggregation via Min() to be performed sequentially. This could also be written as two statements, as well, which would allow us to use the language integrated syntax for the first portion: var tempCollection = from item in collection.AsParallel() let e = item.SomeOperation() where (e.SomeProperty > 6 && e.SomeProperty < 24) select e; double min = tempCollection.AsEnumerable().Min(item => item.PerformComputation()); This allows us to use the standard LINQ style language integrated query syntax, but control whether it’s performed in parallel or serial by adding AsParallel() and AsEnumerable() appropriately. The second important difference between PLINQ and LINQ deals with order preservation.  PLINQ, by default, does not preserve the order of of source collection. This is by design.  In order to process a collection in parallel, the system needs to naturally deal with multiple elements at the same time.  Maintaining the original ordering of the sequence adds overhead, which is, in many cases, unnecessary.  Therefore, by default, the system is allowed to completely change the order of your sequence during processing.  If you are doing a standard query operation, this is usually not an issue.  However, there are times when keeping a specific ordering in place is important.  If this is required, you can explicitly request the ordering be preserved throughout all operations done on a ParallelQuery<T> by using the AsOrdered() extension method.  This will cause our sequence ordering to be preserved. For example, suppose we wanted to take a collection, perform an expensive operation which converts it to a new type, and display the first 100 elements.  In LINQ to Objects, our code might look something like: // Using IEnumerable<SourceClass> collection IEnumerable<ResultClass> results = collection .Select(e => e.CreateResult()) .Take(100); If we just converted this to a parallel query naively, like so: IEnumerable<ResultClass> results = collection .AsParallel() .Select(e => e.CreateResult()) .Take(100); We could very easily get a very different, and non-reproducable, set of results, since the ordering of elements in the input collection is not preserved.  To get the same results as our original query, we need to use: IEnumerable<ResultClass> results = collection .AsParallel() .AsOrdered() .Select(e => e.CreateResult()) .Take(100); This requests that PLINQ process our sequence in a way that verifies that our resulting collection is ordered as if it were processed serially.  This will cause our query to run slower, since there is overhead involved in maintaining the ordering.  However, in this case, it is required, since the ordering is required for correctness. PLINQ is incredibly useful.  It allows us to easily take nearly any LINQ to Objects query and run it in parallel, using the same methods and syntax we’ve used previously.  There are some important differences in operation that must be considered, however – it is not a free pass to parallelize everything.  When using PLINQ in order to parallelize your routines declaratively, the same guideline I mentioned before still applies: Parallelization is something that should be handled with care and forethought, added by design, and not just introduced casually.

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  • Parallelism in .NET – Part 9, Configuration in PLINQ and TPL

    - by Reed
    Parallel LINQ and the Task Parallel Library contain many options for configuration.  Although the default configuration options are often ideal, there are times when customizing the behavior is desirable.  Both frameworks provide full configuration support. When working with Data Parallelism, there is one primary configuration option we often need to control – the number of threads we want the system to use when parallelizing our routine.  By default, PLINQ and the TPL both use the ThreadPool to schedule tasks.  Given the major improvements in the ThreadPool in CLR 4, this default behavior is often ideal.  However, there are times that the default behavior is not appropriate.  For example, if you are working on multiple threads simultaneously, and want to schedule parallel operations from within both threads, you might want to consider restricting each parallel operation to using a subset of the processing cores of the system.  Not doing this might over-parallelize your routine, which leads to inefficiencies from having too many context switches. In the Task Parallel Library, configuration is handled via the ParallelOptions class.  All of the methods of the Parallel class have an overload which accepts a ParallelOptions argument. We configure the Parallel class by setting the ParallelOptions.MaxDegreeOfParallelism property.  For example, let’s revisit one of the simple data parallel examples from Part 2: Parallel.For(0, pixelData.GetUpperBound(0), row => { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } }); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, we’re looping through an image, and calling a method on each pixel in the image.  If this was being done on a separate thread, and we knew another thread within our system was going to be doing a similar operation, we likely would want to restrict this to using half of the cores on the system.  This could be accomplished easily by doing: var options = new ParallelOptions(); options.MaxDegreeOfParallelism = Math.Max(Environment.ProcessorCount / 2, 1); Parallel.For(0, pixelData.GetUpperBound(0), options, row => { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } }); Now, we’re restricting this routine to using no more than half the cores in our system.  Note that I included a check to prevent a single core system from supplying zero; without this check, we’d potentially cause an exception.  I also did not hard code a specific value for the MaxDegreeOfParallelism property.  One of our goals when parallelizing a routine is allowing it to scale on better hardware.  Specifying a hard-coded value would contradict that goal. Parallel LINQ also supports configuration, and in fact, has quite a few more options for configuring the system.  The main configuration option we most often need is the same as our TPL option: we need to supply the maximum number of processing threads.  In PLINQ, this is done via a new extension method on ParallelQuery<T>: ParallelEnumerable.WithDegreeOfParallelism. Let’s revisit our declarative data parallelism sample from Part 6: double min = collection.AsParallel().Min(item => item.PerformComputation()); Here, we’re performing a computation on each element in the collection, and saving the minimum value of this operation.  If we wanted to restrict this to a limited number of threads, we would add our new extension method: int maxThreads = Math.Max(Environment.ProcessorCount / 2, 1); double min = collection .AsParallel() .WithDegreeOfParallelism(maxThreads) .Min(item => item.PerformComputation()); This automatically restricts the PLINQ query to half of the threads on the system. PLINQ provides some additional configuration options.  By default, PLINQ will occasionally revert to processing a query in parallel.  This occurs because many queries, if parallelized, typically actually cause an overall slowdown compared to a serial processing equivalent.  By analyzing the “shape” of the query, PLINQ often decides to run a query serially instead of in parallel.  This can occur for (taken from MSDN): Queries that contain a Select, indexed Where, indexed SelectMany, or ElementAt clause after an ordering or filtering operator that has removed or rearranged original indices. Queries that contain a Take, TakeWhile, Skip, SkipWhile operator and where indices in the source sequence are not in the original order. Queries that contain Zip or SequenceEquals, unless one of the data sources has an originally ordered index and the other data source is indexable (i.e. an array or IList(T)). Queries that contain Concat, unless it is applied to indexable data sources. Queries that contain Reverse, unless applied to an indexable data source. If the specific query follows these rules, PLINQ will run the query on a single thread.  However, none of these rules look at the specific work being done in the delegates, only at the “shape” of the query.  There are cases where running in parallel may still be beneficial, even if the shape is one where it typically parallelizes poorly.  In these cases, you can override the default behavior by using the WithExecutionMode extension method.  This would be done like so: var reversed = collection .AsParallel() .WithExecutionMode(ParallelExecutionMode.ForceParallelism) .Select(i => i.PerformComputation()) .Reverse(); Here, the default behavior would be to not parallelize the query unless collection implemented IList<T>.  We can force this to run in parallel by adding the WithExecutionMode extension method in the method chain. Finally, PLINQ has the ability to configure how results are returned.  When a query is filtering or selecting an input collection, the results will need to be streamed back into a single IEnumerable<T> result.  For example, the method above returns a new, reversed collection.  In this case, the processing of the collection will be done in parallel, but the results need to be streamed back to the caller serially, so they can be enumerated on a single thread. This streaming introduces overhead.  IEnumerable<T> isn’t designed with thread safety in mind, so the system needs to handle merging the parallel processes back into a single stream, which introduces synchronization issues.  There are two extremes of how this could be accomplished, but both extremes have disadvantages. The system could watch each thread, and whenever a thread produces a result, take that result and send it back to the caller.  This would mean that the calling thread would have access to the data as soon as data is available, which is the benefit of this approach.  However, it also means that every item is introducing synchronization overhead, since each item needs to be merged individually. On the other extreme, the system could wait until all of the results from all of the threads were ready, then push all of the results back to the calling thread in one shot.  The advantage here is that the least amount of synchronization is added to the system, which means the query will, on a whole, run the fastest.  However, the calling thread will have to wait for all elements to be processed, so this could introduce a long delay between when a parallel query begins and when results are returned. The default behavior in PLINQ is actually between these two extremes.  By default, PLINQ maintains an internal buffer, and chooses an optimal buffer size to maintain.  Query results are accumulated into the buffer, then returned in the IEnumerable<T> result in chunks.  This provides reasonably fast access to the results, as well as good overall throughput, in most scenarios. However, if we know the nature of our algorithm, we may decide we would prefer one of the other extremes.  This can be done by using the WithMergeOptions extension method.  For example, if we know that our PerformComputation() routine is very slow, but also variable in runtime, we may want to retrieve results as they are available, with no bufferring.  This can be done by changing our above routine to: var reversed = collection .AsParallel() .WithExecutionMode(ParallelExecutionMode.ForceParallelism) .WithMergeOptions(ParallelMergeOptions.NotBuffered) .Select(i => i.PerformComputation()) .Reverse(); On the other hand, if are already on a background thread, and we want to allow the system to maximize its speed, we might want to allow the system to fully buffer the results: var reversed = collection .AsParallel() .WithExecutionMode(ParallelExecutionMode.ForceParallelism) .WithMergeOptions(ParallelMergeOptions.FullyBuffered) .Select(i => i.PerformComputation()) .Reverse(); Notice, also, that you can specify multiple configuration options in a parallel query.  By chaining these extension methods together, we generate a query that will always run in parallel, and will always complete before making the results available in our IEnumerable<T>.

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  • ASP.NET MVC ‘Extendable-hooks’ – ControllerActionInvoker class

    - by nmarun
    There’s a class ControllerActionInvoker in ASP.NET MVC. This can be used as one of an hook-points to allow customization of your application. Watching Brad Wilsons’ Advanced MP3 from MVC Conf inspired me to write about this class. What MSDN says: “Represents a class that is responsible for invoking the action methods of a controller.” Well if MSDN says it, I think I can instill a fair amount of confidence into what the class does. But just to get to the details, I also looked into the source code for MVC. Seems like the base class Controller is where an IActionInvoker is initialized: 1: protected virtual IActionInvoker CreateActionInvoker() { 2: return new ControllerActionInvoker(); 3: } In the ControllerActionInvoker (the O-O-B behavior), there are different ‘versions’ of InvokeActionMethod() method that actually call the action method in question and return an instance of type ActionResult. 1: protected virtual ActionResult InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary<string, object> parameters) { 2: object returnValue = actionDescriptor.Execute(controllerContext, parameters); 3: ActionResult result = CreateActionResult(controllerContext, actionDescriptor, returnValue); 4: return result; 5: } I guess that’s enough on the ‘behind-the-screens’ of this class. Let’s see how we can use this class to hook-up extensions. Say I have a requirement that the user should be able to get different renderings of the same output, like html, xml, json, csv and so on. The user will type-in the output format in the url and should the get result accordingly. For example: http://site.com/RenderAs/ – renders the default way (the razor view) http://site.com/RenderAs/xml http://site.com/RenderAs/csv … and so on where RenderAs is my controller. There are many ways of doing this and I’m using a custom ControllerActionInvoker class (even though this might not be the best way to accomplish this). For this, my one and only route in the Global.asax.cs is: 1: routes.MapRoute("RenderAsRoute", "RenderAs/{outputType}", 2: new {controller = "RenderAs", action = "Index", outputType = ""}); Here the controller name is ‘RenderAsController’ and the action that’ll get called (always) is the Index action. The outputType parameter will map to the type of output requested by the user (xml, csv…). I intend to display a list of food items for this example. 1: public class Item 2: { 3: public int Id { get; set; } 4: public string Name { get; set; } 5: public Cuisine Cuisine { get; set; } 6: } 7:  8: public class Cuisine 9: { 10: public int CuisineId { get; set; } 11: public string Name { get; set; } 12: } Coming to my ‘RenderAsController’ class. I generate an IList<Item> to represent my model. 1: private static IList<Item> GetItems() 2: { 3: Cuisine cuisine = new Cuisine { CuisineId = 1, Name = "Italian" }; 4: Item item = new Item { Id = 1, Name = "Lasagna", Cuisine = cuisine }; 5: IList<Item> items = new List<Item> { item }; 6: item = new Item {Id = 2, Name = "Pasta", Cuisine = cuisine}; 7: items.Add(item); 8: //... 9: return items; 10: } My action method looks like 1: public IList<Item> Index(string outputType) 2: { 3: return GetItems(); 4: } There are two things that stand out in this action method. The first and the most obvious one being that the return type is not of type ActionResult (or one of its derivatives). Instead I’m passing the type of the model itself (IList<Item> in this case). We’ll convert this to some type of an ActionResult in our custom controller action invoker class later. The second thing (a little subtle) is that I’m not doing anything with the outputType value that is passed on to this action method. This value will be in the RouteData dictionary and we’ll use this in our custom invoker class as well. It’s time to hook up our invoker class. First, I’ll override the Initialize() method of my RenderAsController class. 1: protected override void Initialize(RequestContext requestContext) 2: { 3: base.Initialize(requestContext); 4: string outputType = string.Empty; 5:  6: // read the outputType from the RouteData dictionary 7: if (requestContext.RouteData.Values["outputType"] != null) 8: { 9: outputType = requestContext.RouteData.Values["outputType"].ToString(); 10: } 11:  12: // my custom invoker class 13: ActionInvoker = new ContentRendererActionInvoker(outputType); 14: } Coming to the main part of the discussion – the ContentRendererActionInvoker class: 1: public class ContentRendererActionInvoker : ControllerActionInvoker 2: { 3: private readonly string _outputType; 4:  5: public ContentRendererActionInvoker(string outputType) 6: { 7: _outputType = outputType.ToLower(); 8: } 9: //... 10: } So the outputType value that was read from the RouteData, which was passed in from the url, is being set here in  a private field. Moving to the crux of this article, I now override the CreateActionResult method. 1: protected override ActionResult CreateActionResult(ControllerContext controllerContext, ActionDescriptor actionDescriptor, object actionReturnValue) 2: { 3: if (actionReturnValue == null) 4: return new EmptyResult(); 5:  6: ActionResult result = actionReturnValue as ActionResult; 7: if (result != null) 8: return result; 9:  10: // This is where the magic happens 11: // Depending on the value in the _outputType field, 12: // return an appropriate ActionResult 13: switch (_outputType) 14: { 15: case "json": 16: { 17: JavaScriptSerializer serializer = new JavaScriptSerializer(); 18: string json = serializer.Serialize(actionReturnValue); 19: return new ContentResult { Content = json, ContentType = "application/json" }; 20: } 21: case "xml": 22: { 23: XmlSerializer serializer = new XmlSerializer(actionReturnValue.GetType()); 24: using (StringWriter writer = new StringWriter()) 25: { 26: serializer.Serialize(writer, actionReturnValue); 27: return new ContentResult { Content = writer.ToString(), ContentType = "text/xml" }; 28: } 29: } 30: case "csv": 31: controllerContext.HttpContext.Response.AddHeader("Content-Disposition", "attachment; filename=items.csv"); 32: return new ContentResult 33: { 34: Content = ToCsv(actionReturnValue as IList<Item>), 35: ContentType = "application/ms-excel" 36: }; 37: case "pdf": 38: string filePath = controllerContext.HttpContext.Server.MapPath("~/items.pdf"); 39: controllerContext.HttpContext.Response.AddHeader("content-disposition", 40: "attachment; filename=items.pdf"); 41: ToPdf(actionReturnValue as IList<Item>, filePath); 42: return new FileContentResult(StreamFile(filePath), "application/pdf"); 43:  44: default: 45: controllerContext.Controller.ViewData.Model = actionReturnValue; 46: return new ViewResult 47: { 48: TempData = controllerContext.Controller.TempData, 49: ViewData = controllerContext.Controller.ViewData 50: }; 51: } 52: } A big method there! The hook I was talking about kinda above actually is here. This is where different kinds / formats of output get returned based on the output type requested in the url. When the _outputType is not set (string.Empty as set in the Global.asax.cs file), the razor view gets rendered (lines 45-50). This is the default behavior in most MVC applications where-in a view (webform/razor) gets rendered on the browser. As you see here, this gets returned as a ViewResult. But then, for an outputType of json/xml/csv, a ContentResult gets returned, while for pdf, a FileContentResult is returned. Here are how the different kinds of output look like: This is how we can leverage this feature of ASP.NET MVC to developer a better application. I’ve used the iTextSharp library to convert to a pdf format. Mike gives quite a bit of detail regarding this library here. You can download the sample code here. (You’ll get an option to download once you open the link). Verdict: Hot chocolate: $3; Reebok shoes: $50; Your first car: $3000; Being able to extend a web application: Priceless.

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  • C#: Adding Functionality to 3rd Party Libraries With Extension Methods

    - by James Michael Hare
    Ever have one of those third party libraries that you love but it's missing that one feature or one piece of syntactical candy that would make it so much more useful?  This, I truly think, is one of the best uses of extension methods.  I began discussing extension methods in my last post (which you find here) where I expounded upon what I thought were some rules of thumb for using extension methods correctly.  As long as you keep in line with those (or similar) rules, they can often be useful for adding that little extra functionality or syntactical simplification for a library that you have little or no control over. Oh sure, you could take an open source project, download the source and add the methods you want, but then every time the library is updated you have to re-add your changes, which can be cumbersome and error prone.  And yes, you could possibly extend a class in a third party library and override features, but that's only if the class is not sealed, static, or constructed via factories. This is the perfect place to use an extension method!  And the best part is, you and your development team don't need to change anything!  Simply add the using for the namespace the extensions are in! So let's consider this example.  I love log4net!  Of all the logging libraries I've played with, it, to me, is one of the most flexible and configurable logging libraries and it performs great.  But this isn't about log4net, well, not directly.  So why would I want to add functionality?  Well, it's missing one thing I really want in the ILog interface: ability to specify logging level at runtime. For example, let's say I declare my ILog instance like so:     using log4net;     public class LoggingTest     {         private static readonly ILog _log = LogManager.GetLogger(typeof(LoggingTest));         ...     }     If you don't know log4net, the details aren't important, just to show that the field _log is the logger I have gotten from log4net. So now that I have that, I can log to it like so:     _log.Debug("This is the lowest level of logging and just for debugging output.");     _log.Info("This is an informational message.  Usual normal operation events.");     _log.Warn("This is a warning, something suspect but not necessarily wrong.");     _log.Error("This is an error, some sort of processing problem has happened.");     _log.Fatal("Fatals usually indicate the program is dying hideously."); And there's many flavors of each of these to log using string formatting, to log exceptions, etc.  But one thing there isn't: the ability to easily choose the logging level at runtime.  Notice, the logging levels above are chosen at compile time.  Of course, you could do some fun stuff with lambdas and wrap it, but that would obscure the simplicity of the interface.  And yes there is a Logger property you can dive down into where you can specify a Level, but the Level properties don't really match the ILog interface exactly and then you have to manually build a LogEvent and... well, it gets messy.  I want something simple and sexy so I can say:     _log.Log(someLevel, "This will be logged at whatever level I choose at runtime!");     Now, some purists out there might say you should always know what level you want to log at, and for the most part I agree with them.  For the most party the ILog interface satisfies 99% of my needs.  In fact, for most application logging yes you do always know the level you will be logging at, but when writing a utility class, you may not always know what level your user wants. I'll tell you, one of my favorite things is to write reusable components.  If I had my druthers I'd write framework libraries and shared components all day!  And being able to easily log at a runtime-chosen level is a big need for me.  After all, if I want my code to really be re-usable, I shouldn't force a user to deal with the logging level I choose. One of my favorite uses for this is in Interceptors -- I'll describe Interceptors in my next post and some of my favorites -- for now just know that an Interceptor wraps a class and allows you to add functionality to an existing method without changing it's signature.  At the risk of over-simplifying, it's a very generic implementation of the Decorator design pattern. So, say for example that you were writing an Interceptor that would time method calls and emit a log message if the method call execution time took beyond a certain threshold of time.  For instance, maybe if your database calls take more than 5,000 ms, you want to log a warning.  Or if a web method call takes over 1,000 ms, you want to log an informational message.  This would be an excellent use of logging at a generic level. So here was my personal wish-list of requirements for my task: Be able to determine if a runtime-specified logging level is enabled. Be able to log generically at a runtime-specified logging level. Have the same look-and-feel of the existing Debug, Info, Warn, Error, and Fatal calls.    Having the ability to also determine if logging for a level is on at runtime is also important so you don't spend time building a potentially expensive logging message if that level is off.  Consider an Interceptor that may log parameters on entrance to the method.  If you choose to log those parameter at DEBUG level and if DEBUG is not on, you don't want to spend the time serializing those parameters. Now, mine may not be the most elegant solution, but it performs really well since the enum I provide all uses contiguous values -- while it's never guaranteed, contiguous switch values usually get compiled into a jump table in IL which is VERY performant - O(1) - but even if it doesn't, it's still so fast you'd never need to worry about it. So first, I need a way to let users pass in logging levels.  Sure, log4net has a Level class, but it's a class with static members and plus it provides way too many options compared to ILog interface itself -- and wouldn't perform as well in my level-check -- so I define an enum like below.     namespace Shared.Logging.Extensions     {         // enum to specify available logging levels.         public enum LoggingLevel         {             Debug,             Informational,             Warning,             Error,             Fatal         }     } Now, once I have this, writing the extension methods I need is trivial.  Once again, I would typically /// comment fully, but I'm eliminating for blogging brevity:     namespace Shared.Logging.Extensions     {         // the extension methods to add functionality to the ILog interface         public static class LogExtensions         {             // Determines if logging is enabled at a given level.             public static bool IsLogEnabled(this ILog logger, LoggingLevel level)             {                 switch (level)                 {                     case LoggingLevel.Debug:                         return logger.IsDebugEnabled;                     case LoggingLevel.Informational:                         return logger.IsInfoEnabled;                     case LoggingLevel.Warning:                         return logger.IsWarnEnabled;                     case LoggingLevel.Error:                         return logger.IsErrorEnabled;                     case LoggingLevel.Fatal:                         return logger.IsFatalEnabled;                 }                                 return false;             }             // Logs a simple message - uses same signature except adds LoggingLevel             public static void Log(this ILog logger, LoggingLevel level, object message)             {                 switch (level)                 {                     case LoggingLevel.Debug:                         logger.Debug(message);                         break;                     case LoggingLevel.Informational:                         logger.Info(message);                         break;                     case LoggingLevel.Warning:                         logger.Warn(message);                         break;                     case LoggingLevel.Error:                         logger.Error(message);                         break;                     case LoggingLevel.Fatal:                         logger.Fatal(message);                         break;                 }             }             // Logs a message and exception to the log at specified level.             public static void Log(this ILog logger, LoggingLevel level, object message, Exception exception)             {                 switch (level)                 {                     case LoggingLevel.Debug:                         logger.Debug(message, exception);                         break;                     case LoggingLevel.Informational:                         logger.Info(message, exception);                         break;                     case LoggingLevel.Warning:                         logger.Warn(message, exception);                         break;                     case LoggingLevel.Error:                         logger.Error(message, exception);                         break;                     case LoggingLevel.Fatal:                         logger.Fatal(message, exception);                         break;                 }             }             // Logs a formatted message to the log at the specified level.              public static void LogFormat(this ILog logger, LoggingLevel level, string format,                                          params object[] args)             {                 switch (level)                 {                     case LoggingLevel.Debug:                         logger.DebugFormat(format, args);                         break;                     case LoggingLevel.Informational:                         logger.InfoFormat(format, args);                         break;                     case LoggingLevel.Warning:                         logger.WarnFormat(format, args);                         break;                     case LoggingLevel.Error:                         logger.ErrorFormat(format, args);                         break;                     case LoggingLevel.Fatal:                         logger.FatalFormat(format, args);                         break;                 }             }         }     } So there it is!  I didn't have to modify the log4net source code, so if a new version comes out, i can just add the new assembly with no changes.  I didn't have to subclass and worry about developers not calling my sub-class instead of the original.  I simply provide the extension methods and it's as if the long lost extension methods were always a part of the ILog interface! Consider a very contrived example using the original interface:     // using the original ILog interface     public class DatabaseUtility     {         private static readonly ILog _log = LogManager.Create(typeof(DatabaseUtility));                 // some theoretical method to time         IDataReader Execute(string statement)         {             var timer = new System.Diagnostics.Stopwatch();                         // do DB magic                                    // this is hard-coded to warn, if want to change at runtime tough luck!             if (timer.ElapsedMilliseconds > 5000 && _log.IsWarnEnabled)             {                 _log.WarnFormat("Statement {0} took too long to execute.", statement);             }             ...         }     }     Now consider this alternate call where the logging level could be perhaps a property of the class          // using the original ILog interface     public class DatabaseUtility     {         private static readonly ILog _log = LogManager.Create(typeof(DatabaseUtility));                 // allow logging level to be specified by user of class instead         public LoggingLevel ThresholdLogLevel { get; set; }                 // some theoretical method to time         IDataReader Execute(string statement)         {             var timer = new System.Diagnostics.Stopwatch();                         // do DB magic                                    // this is hard-coded to warn, if want to change at runtime tough luck!             if (timer.ElapsedMilliseconds > 5000 && _log.IsLogEnabled(ThresholdLogLevel))             {                 _log.LogFormat(ThresholdLogLevel, "Statement {0} took too long to execute.",                     statement);             }             ...         }     } Next time, I'll show one of my favorite uses for these extension methods in an Interceptor.

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  • What is Polymorphism?

    - by SAMIR BHOGAYTA
    * Polymorphism is one of the primary characteristics (concept) of object-oriented programming. * Poly means many and morph means form. Thus, polymorphism refers to being able to use many forms of a type without regard to the details. * Polymorphism is the characteristic of being able to assign a different meaning specifically, to allow an entity such as a variable, a function, or an object to have more than one form. * Polymorphism is the ability to process objects differently depending on their data types. * Polymorphism is the ability to redefine methods for derived classes. Types of Polymorphism * Compile time Polymorphism * Run time Polymorphism Compile time Polymorphism * Compile time Polymorphism also known as method overloading * Method overloading means having two or more methods with the same name but with different signatures Example of Compile time polymorphism public class Calculations { public int add(int x, int y) { return x+y; } public int add(int x, int y, int z) { return x+y+z; } } Run time Polymorphism * Run time Polymorphism also known as method overriding * Method overriding means having two or more methods with the same name , same signature but with different implementation Example of Run time Polymorphism class Circle { public int radius = 0; public double getArea() { return 3.14 * radius * radius } } class Sphere { public double getArea() { return 4 * 3.14 * radius * radius } }

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