Search Results

Search found 5903 results on 237 pages for 'generic variance'.

Page 62/237 | < Previous Page | 58 59 60 61 62 63 64 65 66 67 68 69  | Next Page >

  • Internet Timeouts with TP-Link TL-WN821N v2 wireless usb stick

    - by user1622959
    A short time after accessing the internet, the browser/download times out. Before the timeout, the internet works OK briefly; afterwards, the wireless is still connected with a strong signal, but every internet access results in a timeout. When I leave the PC for a while, the internet is back just to timeout again as soon as I start using it. The same happens when I reconnect to the router. Also, when I surf the internet, it takes a couple of minutes until the timeout, but when I download something, it times out in a matter of seconds. The wireless adapter works just fine in Windows and internet via ethernet cable works just fine in Ubuntu. Does anyone have the same problem or knows a solution. I use Ubuntu 12.10 x64. The problem occurs since I installed ubuntu (which was a few days ago). Here some stuff that might be usefull: serus@serus-Ubuntu-PC:~$ lsusb Bus 002 Device 002: ID 0cf3:1002 Atheros Communications, Inc. TP-Link TL-WN821N v2 802.11n [Atheros AR9170] serus@serus-Ubuntu-PC:~$ lsmod Module Size Used by carl9170 82083 0 serus@serus-Ubuntu-PC:~$ modinfo carl9170 filename: /lib/modules/3.5.0-21- generic/kernel/drivers/net/wireless/ath/carl9170/carl9170.ko alias: arusb_lnx alias: ar9170usb firmware: carl9170-1.fw description: Atheros AR9170 802.11n USB wireless serus@serus-Ubuntu-PC:~$ iwconfig wlan0 IEEE 802.11bgn ESSID:"virginmedia0137463" Mode:Managed Frequency:2.462 GHz Access Point: A0:21:B7:F8:29:B6 Bit Rate=240 Mb/s Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=66/70 Signal level=-44 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:1399 Invalid misc:18 Missed beacon:0 serus@serus-Ubuntu-PC:~$ sudo lshw -C network *-network description: Wireless interface physical id: 1 bus info: usb@2:2 logical name: wlan0 serial: 00:27:19:bb:00:19 capabilities: ethernet physical wireless configuration: broadcast=yes driver=carl9170 driverversion=3.5.0-21-generic firmware=1.9.4 ip=192.168.0.6 link=yes multicast=yes wireless=IEEE 802.11bgn

    Read the article

  • Ubuntu Server 11.10 boot, white terminal with garbled black text

    - by SpeedCrazy
    I just installed Ubuntu server 11.10 and the install went fine. This system is running on an Intel Pentium II board with onboard graphics. However when I try to boot into Ubuntu I get a white terminal with garbled black text. I have tried various grub 'fixes' as googling the issue seemed to suggest it was a res or grub related issue. I cannot ssh in so the issue does affect Linux as well. I have had no luck with anything thus far and am at my wits end. This was my first Ubuntu excursion as my friend told me it was better for servers than CentOS because it was easier... Not so much.... Does anyone have any ideas as to what the issue could be? When answering bear in mind I am an Ubuntu noob and Linux novice. As of 1/26/12 I have tried to add the console=ttyl line to the /etc/default/grub and run update-grub. This results in the line in the boot parameters that normally reads: linux /vmlunz-3.0.0-12-generic-pae root=/dev/mapper/dev-root rovt.handoff=7 now reads: linux /vmlunz-3.0.0-12-generic-pae root=/dev/mapper/dev-root ro console=ttyl vt.handoff=7 This does not work. Is there anyway to have console=ttyl inserted on a line by itself? I am at my wits ends, Thanks for all your help, Speed

    Read the article

  • Where to install boot loader on a Zenbook Prime?

    - by Christians
    I cannot figure out where to install the boot loader on my Zenbook UX31A Prime. I have installed Ubuntu many times on normal hard drives, but this is the first SSD and I am struggling. Installed Ubuntu 12.04 64-bit selecting "UEFI: general" boot entry. Installation type: Something Else Created partition /sda5 mount as /, /sda6 mount as /home, /sda7 mount as swap Selected /dev/sda for boot loader installation. Other options are /dev/sda, /dev/sda1/dev/sda3 Windows 7 (loader) ... Grub comes up with 6 entries Ubuntu - this runs great Linux 3.2.0-29-generic recovery mode: mode hangs with "fb: conflicting fb hw usae interdrnfb vs EFI VGA - removing generic adapter" memtest86:erro: unknown command `linux 16' memtest86 serial: unknown command `linux 16' Windows 7 (loader) (on /dev/sda3): invalid EFI file path Windows Recovery Environment (on /dev/sda8): unknown command drivemap, invalid EFI file path. My workaround for booting Windows 7 is hitting ESC during boot, windows boot manager comes up and * for booting into Windows 7 I select "WIndows Boot Manager (PO: SanDisk ....". * for booting into Ubuntu I select ubuntu (P0: SanDisk...) How can I boot into Windows from Grub?

    Read the article

  • Ubuntu 12.04 slow boot on ASUS, attached with dmesg and bootchart

    - by stanleyhunk
    I heard that Ubuntu can boot up around 30sec, but I take more than 60sec every time my Ubuntu boot. I also read some forum said need to post the dmesg and bootchart to identify which process slowing down the booting time, as I'm not expert in Ubuntu and wish to learn more about it, I humbly ask any pro here to teach me how. My laptop specs: Model : ASUS K45VS RAM : 8MB CPU : Intel(R) Core(TM) i7-3630QM CPU @ 2.40GHz x 8 Graphic Card : nVidia GeForce GT 645M HDD : 750GB OS : Single boot Ubuntu 12.04LTS System.uname : Linux 3.8.0-39-generic #58~precise1-Ubuntu SMP Fri May 2 21:33:40 UTC 2014 x86_64 System.release : Ubuntu 12.04.4 LTS System.kernel.options : BOOT_IMAGE=/boot/vmlinuz-3.8.0-39-generic root=UUID=c8a71503-bce8-406c-9a5f-5aa8284f5c7c ro quiet splash My dmesg (which highlighted to the huge time frame gap): [ 30.772656] cgroup: libvirtd (1961) created nested cgroup for controller "memory" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 30.772659] cgroup: "memory" requires setting use_hierarchy to 1 on the root. [ 30.772683] cgroup: libvirtd (1961) created nested cgroup for controller "devices" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 30.772710] cgroup: libvirtd (1961) created nested cgroup for controller "blkio" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 32.140335] nvidia 0000:01:00.0: irq 46 for MSI/MSI-X [ 32.505619] ACPI Error: Field [TMPB] at 1081344 exceeds Buffer [ROM1] size 262144 (bits) (20121018/dsopcode-236) [ 32.505624] ACPI Error: Method parse/execution failed [\_SB_.PCI0.PEG0.PEGP._ROM] (Node ffff880224e91f00), AE_AML_BUFFER_LIMIT (20121018/psparse-537) [ 802.034422] audit_printk_skb: 69 callbacks suppressed [ 802.034428] type=1400 audit(1400914804.392:35): apparmor="DENIED" operation="capable" parent=1 profile="/usr/sbin/cupsd" pid=1683 comm="cupsd" pid=1683 comm="cupsd" capability=36 capname="block_suspend" [ 1581.300901] type=1400 audit(1400915584.816:36): apparmor="DENIED" operation="capable" parent=1 profile="/usr/sbin/cupsd" pid=1683 comm="cupsd" pid=1683 comm="cupsd" capability=36 capname="block_suspend" My Bootchart.png: Looking forward to learn to improve both my booting time and knowledge. Thanks in advance :)

    Read the article

  • wrong kernel running after install

    - by ticktockhouse
    I have installed Ubuntu 14.04 from unetbootin. When it reboots after the install, uname -r says: 3.5.0-17-generic ..this means that no modules have loaded for the kernel that is actually installed (3.13.0-32-generic). Does anyone know why this kernel should be installed via the install process? Is it an artifact of using Unetbootin? Booting into the Unetbootin image gives the correct kernel, and thus the modules load. Knowing why is one thing, but I'm not sure how to remedy it now. Because no modules are loaded, I can't connect to the network or connect a USB drive. I've tried update-grub, which seems to find the correct kernel, but doesn't seem to tell the system to boot from it. I've also tried selecting the kernel at boot time using the "Advanced Options for Ubuntu", and the 3.13.x kernel is the only one listed. Selecting this lead to the 3.5.x kernel stubbornly loading.. I'm a fairly accomplished sysadmin, but this one has me flummoxed :) Can anyone help?

    Read the article

  • Audio comes out of both headphone and speaker at the same time.. Ubuntu 12.04LTS [closed]

    - by pst007x
    I have the same issue on an Aspire. Ubuntu 12.04LTS 64bit realtek audio sound chip onboard If I plug in a headset, audio does not switch from internal speaker to headset, instead plays out of both at the same time. I have looked at the alsamixer setting, all on. I installed gnome-alsamixer, and I noticed headphone was ticked, if I untick the main audio mutes, and the headphone no longer works. Headset only works with internal speaker. Audio works fine on my other desktop and laptop running this release 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03) salvatore@salvatore-Aspire-7730:~$ cat /proc/asound/version Advanced Linux Sound Architecture Driver Version 1.0.24. salvatore@salvatore-Aspire-7730:~$ head -n 1 /proc/asound/card*/codec#* ==> /proc/asound/card0/codec#0 <== Codec: Realtek ALC888 ==> /proc/asound/card0/codec#1 <== Codec: LSI ID 1040 ==> /proc/asound/card0/codec#2 <== Codec: Intel Cantiga HDMI salvatore@salvatore-Aspire-7730:~$ aplay -l **** List of PLAYBACK Hardware Devices **** card 0: Intel [HDA Intel], device 0: ALC888 Analog [ALC888 Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: Intel [HDA Intel], device 1: ALC888 Digital [ALC888 Digital] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: Intel [HDA Intel], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 salvatore@salvatore-Aspire-7730:~$ uname -a Linux salvatore-Aspire-7730 3.2.0-23-generic #36-Ubuntu SMP Tue Apr 10 20:39:51 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux salvatore@salvatore-Aspire-7730:~$ The alsa-base.conf does not exist Tried this: sudo apt-get remove --purge alsa-base sudo apt-get remove --purge pulseaudio sudo apt-get install alsa-base sudo apt-get install pulseaudio sudo alsa force-reload Then: sudo apt-get purge pulseaudio gstreamer0.10-pulseaudio sudo apt-get install pulseaudio gstreamer0.10-pulseaudio indicator-sound Tred this. sudo gedit Then open terminal: sudo /etc/modprobe.d/alsa-base.conf At the end of the file add a new line: options snd-hda-intel model=generic Save and then reboot But alsa-base.conf does not exist

    Read the article

  • Is error suppression acceptable in role of logic mechanism?

    - by Rarst
    This came up in code review at work in context of PHP and @ operator. However I want to try keep this in more generic form, since few question about it I found on SO got bogged down in technical specifics. Accessing array field, which is not set, results in error message and is commonly handled by following logic (pseudo code): if field value is set output field value Code in question was doing it like: start ignoring errors output field value stop ignoring errors The reasoning for latter was that it's more compact and readable code in this specific case. I feel that those benefits do not justify misuse (IMO) of language mechanics. Is such code is being "clever" in a bad way? Is discarding possible error (for any reason) acceptable practice over explicitly handling it (even if that leads to more extensive and/or intensive code)? Is it acceptable for programming operators to cross boundaries of intended use (like in this case using error handling for controlling output)? Edit I wanted to keep it more generic, but specific code being discussed was like this: if ( isset($array['field']) ) { echo '<li>' . $array['field'] . '</li>'; } vs the following example: echo '<li>' . @$array['field'] . '</li>';

    Read the article

  • VMware9 fails to launch Virtual OS. Ubuntu 12.10 64bit (Unable to change virtual machine power state: Pipe connection has been broken.)

    - by pst007x
    Another issue I need help with. I use VMware for work on Ubuntu 12.04. However for some reasons my VMware Workstation software generates the following error: Unable to change virtual machine power state: Failed to power on '/home/pst007x/vmware/Windows 7 x64/Windows 7 x64.vmx'. Transport (VMDB) error -14: Pipe connection has been broken. Product: VMware® Workstation Version: 9.0.0 build-812388 Host OS Version: 3.5.0-18-generic Ubuntu 12.10 64bit Kernel Linux 3.5.0-18-generic I have seen patches, but nothing works, and the patches are not maintained, broken links. PLEASE NOTE: I know that this has been asked, but there was no answer given that resolves this issue. Unfortunately I have changed all my office and personal PC's to Ubuntu, and use Win7 in a vm, however since 12.10, vm now fails to launch. For me this is a catastrophe, and makes Ubuntu useless for me to use! I am in a desperate situation here, is there is anyone that can offer any help I would be truly appreciative. I have looked on the VMware forums and the only solution is offered for Fedora, but the people posting there are not clear about what the solution is! thanks PLEASE DO NOT CLOSE THIS QUESTION! I have tried everywhere to find a solution, but I have come up blank... Patches referenced to in other posts do not work in this version of VMware...

    Read the article

  • How to remove the last character from Stringbuilder

    - by hmloo
    We usually use StringBuilder to append string in loops and make a string of each data separated by a delimiter. but you always end up with an extra delimiter at the end. This code sample shows how to remove the last delimiter from a StringBuilder. using System; using System.Collections.Generic; using System.Text; using System.Linq; class Program { static void Main() { var list =Enumerable.Range(0, 10).ToArray(); StringBuilder sb = new StringBuilder(); foreach(var item in list) { sb.Append(item).Append(","); } sb.Length--;//Just reduce the length of StringBuilder, it's so easy Console.WriteLine(sb); } } //Output : 0,1,2,3,4,5,6,7,8,9 Alternatively,  we can use string.Join for the same results, please refer to blow code sample. using System; using System.Collections.Generic; using System.Text; using System.Linq; class Program { static void Main() { var list = Enumerable.Range(0, 10).Select(n => n.ToString()).ToArray(); string str = string.Join(",", list); Console.WriteLine(str); } }

    Read the article

  • I can't hear any sounds on ubuntu 11.10 on Dell inspiron N5010

    - by Ahmed
    I have a problem that I can't hear any sounds and I don't know where to start. I did the following : lspci -v | grep -A7 -i "audio" 00:1b.0 Audio device: Intel Corporation 5 Series/3400 Series Chipset High Definition Audio (rev 06) Subsystem: Dell Device 0447 Flags: bus master, fast devsel, latency 0, IRQ 48 Memory at fbf00000 (64-bit, non-prefetchable) [size=16K] Capabilities: <access denied> Kernel driver in use: HDA Intel Kernel modules: snd-hda-intel -- 01:00.1 Audio device: ATI Technologies Inc Manhattan HDMI Audio [Mobility Radeon HD 5000 Series] Subsystem: Dell Device 0447 Flags: bus master, fast devsel, latency 0, IRQ 49 Memory at fbe40000 (64-bit, non-prefetchable) [size=16K] Capabilities: <access denied> Kernel driver in use: HDA Intel Kernel modules: snd-hda-intel And It seems that I have 2 soundcards. Is that normal ?? I also did this: aplay -l **** List of PLAYBACK Hardware Devices **** card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 1: Generic [HD-Audio Generic], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 Also on the sound setting GUI. I have 2 hardware profiles for sound cards but none of them works when I test the speakers. Where should I start searching ?

    Read the article

  • When can I publish a software tool written at work?

    - by AlexMA
    I'm working on a software problem at work that is fairly generic, but I can't find a library I like to solve it, so I'm considering writing one myself (at least a bare-bones version). I'll be writing some if not all of the 1.0 version at work, since I need it for the project. If turns out well I might want to bring the work home and polish it up just for fun, and maybe release it as an open-source project. However, I'm concerned that if I wrote the 1.0 version at work I may not be allowed to do this from a legal sense. Obviously I could ask my boss (who probably won't care), but I'm curious how other programmers have dealt with this issue and where the law stands here. My one sentence question is, When is it okay (legally/ethically) to open-source a software tool originally written by you for work at work? What if you have expanded the original source significantly during off-hours? Follow-up: Suppose I write the whole thing at home on my time then simply use it at work, does that change things drastically? Follow-up 2: Note that I'm not trying to rip off my employer (I understand that they're paying me to build products that they own)--I'm just wondering if there's a fair way of doing this for all involved... It would be nice if some nonprofit down the road could use my code and save them some time. Also, there's another issue at stake. If I write the library for a very simple, generic thing (like HTML tables in Javascript), does that mean I can never again do so on my own time without putting myself at legal risk (even if it was a whole new fresh rewrite or a segment of a larger project). Am I surrendering my right to write code for this sort of project for the rest of my life (without this company's permission), since the code at work might still be somewhere in my brain influencing me? This seems related to software patents, as a side-note.

    Read the article

  • Point an external domain to a shared hosting website

    - by dailgez004
    I bought a domain from a seller (GoDaddy), and wish to point it at a shared hosting website (ASmallOrange). Googling tells me it's fairly straightforward: Step 1: On the external domain's DNS, configure two NS records for the two nameservers of the hosting service. Step 2: Wait 2-48 hours. I'm puzzled because it can't be that simple. I've told the DNS where to look, but since it's shared hosting, the hosting service needs to know what site to point the domain to. And indeed, after I've performed the above steps, visiting the domain leads me to a generic message from the shared hosting service. Okay, so I have to configure the DNS on the hosting service, right? The service I use (ASmallOrange) uses cPanel. What I tried is to set up a Parked Domain for the externally bought domain; when I go into the Advanced DNS Zone Editor, sure enough, the DNS for the external domain shows up as something I can configure. Yet, visiting the externally registered domain still points me to the generic shared server page. I'm convinced I'm doing something wrong. Could someone debug my thought process? Or perhaps offer alternate solutions? Right now, I'm considering trying to set up a CNAME record on the external domain to point to the domain I registered through the shared host -- but I have a vague impression that this is bad practice.

    Read the article

  • Why am I getting this error while installing gnome?

    - by Sreehari Rajendran
    i have raring ringtail. I installed gnome a couple days ago. I try to install extensions but the site says I don't have the latest version. I type the command sudo apt-get install gnome-shell and I get this error Reading package lists... Done Building dependency tree Reading state information... Done gnome-shell is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 138 not upgraded. 1 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Do you want to continue [Y/n]? y Setting up initramfs-tools (0.103ubuntu0.7) ... update-initramfs: deferring update (trigger activated) Processing triggers for initramfs-tools ... update-initramfs: Generating /boot/initrd.img-3.8.0-25-generic cp: cannot stat ‘/module-files.d/libpango1.0-0.modules’: No such file or directory cp: cannot stat ‘/modules/pango-basic-fc.so’: No such file or directory E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1. update-initramfs: failed for /boot/initrd.img-3.8.0-25-generic with 1. dpkg: error processing initramfs-tools (--configure): subprocess installed post-installation script returned error exit status 1 No apport report written because MaxReports is reached already Errors were encountered while processing: initramfs-tools E: Sub-process /usr/bin/dpkg returned an error code (1) why?

    Read the article

  • Integrating Amazon EC2 in Java via NetBeans IDE

    - by Geertjan
    Next, having looked at Amazon Associates services and Amazon S3, let's take a look at Amazon EC2, the elastic compute cloud which provides remote computing services. I started by launching an instance of Ubuntu Server 14.04 on Amazon EC2, which looks a bit like this in the on-line AWS Management Console, though I whitened out most of the details: Now that I have at least one running instance available on Amazon EC2, it makes sense to use the services that are integrated into NetBeans IDE:  I created a new application with one class, named "AmazonEC2Demo". Then I dragged the "describeInstances" service that you see above, with the mouse, into the class. Then the IDE automatically created all the other files you see below, i.e., 4 Java classes and one properties file: In the properties file, register the access ID and secret keys. These are read by the other generated Java classes. Signing and authentication are done automatically by the code that is generated, i.e., there's nothing generic you need to do and you can immediately begin working on your domain-specific code. Finally, you're now able to rewrite the code in "AmazonEC2Demo" to connect to Amazon EC2 and obtain information about your running instance: public class AmazonEC2Demo { public static void main(String[] args) { String instanceId1 = "i-something"; RestResponse result; try { result = AmazonEC2Service.describeInstances(instanceId1); System.out.println(result.getDataAsString()); } catch (IOException ex) { Logger.getLogger(AmazonEC2Demo.class.getName()).log(Level.SEVERE, null, ex); } } } From the above, you'll receive a chunk of XML with data about the running instance, it's name, status, dates, etc. In other words, you're now ready to integrate Amazon EC2 features directly into the applications you're writing, without very much work to get started. Within about 5 minutes, you're working on your business logic, rather than on the generic code that anyone needs when integrating with Amazon EC2.

    Read the article

  • Using onboard and pci-e graphics card at the same time

    - by Endle
    Hello wonderful people. I know there are several other posts with similar questions. I also know how to use Google. I also have read up on posts discussing bumblebee, crossfire, ati catylist and many other interesting topics. I would just like someone to give me advice on how to use the onboard and pci-e graphics at the same time. I know the computer is capable of doing this. It works in Windows. I can use the VGA and DVI onboard port and the HDMI port of the add on card all at the same time. Works great in Windows 7, In Ubuntu, it seems only one or the other will work. I can use any combination of two displays on either adapter: VGA and HDMI..HDMI and DVI..so forth and so on. I have started experimenting with xorg.conf files, but have not been able to get any of them to work. Here is my last attempt at writing an xorg.conf file: Section "ServerLayout" Identifier "X.org Configured" Screen 0 "Screen0" 0 0 Screen 1 "Screen1" LeftOf "Screen0" Screen 2 "Screen2" LeftOf "Screen1" InputDevice "Mouse0" "CorePointer" InputDevice "Keyboard0" "CoreKeyboard" EndSection Section "Device" Identifier "Onboard Video" Driver "radeon" BusID "PCI:01:05.0" EndSection Section "Device" Identifier "Graphics Card" Driver "radeon" BusID "PCI:02:00.0" EndSection Section "Monitor" Identifier "CRT2" Option "VendorName" "ViewSonic" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection Section "Monitor" Identifier "DVI1" VendorName "ACR" ModelName "P224W" Option "DPMS" EndSection Section "Monitor" Identifier "DVI2" Option "VendorName" "Acer" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection Section "Screen" Identifier "Screen0" Device "Onboard Video" Monitor "CRT2" DefaultDepth 24 SubSection "Display" Depth 24 Modes "1280x1024" EndSubSection EndSection Section "Screen" Identifier "Screen1" Device "Graphics Card" Monitor "DVI1" DefaultDepth 24 SubSection "Display" Depth 24 Modes "1920x1080" EndSubSection

    Read the article

  • Uninstall ax88179 package

    - by jackbenny
    I've installed the ax88179 package from the PPA (since the ax88179 driver isn't in the 3.8 kernel). But now I'd like to install kernel 3.11.6 and this module is already included here. So I'd like to uninstall the the module from the package but this fails with the following error message The following packages will be REMOVED: ax88179* 0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded. After this operation, 313 kB disk space will be freed. Do you want to continue [Y/n]? (Reading database ... 202833 files and directories currently installed.) Removing ax88179 ... Error! There are no instances of module: ax88179_178a 1.6.0 located in the DKMS tree. rm: cannot remove ‘/usr/src/AX88179_178A_LINUX_DRIVER_v1.6.0_SOURCE’: No such file or directory dpkg: error processing ax88179 (--purge): subprocess installed pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already ln: failed to create symbolic link ‘/usr/src/AX88179_178A_LINUX_DRIVER_v1.7.0_SOURCE’: File exists Error! DKMS tree already contains: ax88179_178a-1.7.0 You cannot add the same module/version combo more than once. Module ax88179_178a/1.7.0 already built for kernel 3.8.0-32-generic/4 Module ax88179_178a/1.7.0 already installed on kernel 3.8.0-32-generic/x86_64 Errors were encountered while processing: ax88179 E: Sub-process /usr/bin/dpkg returned an error code (1) It complains about both version 1.6 and 1.7. I've updated to 1.7 a couple of days ago. --force doesn't help either. I just want to get rid of it since when I'm running 3.11.6 the versions interfere with each other.

    Read the article

  • Oracle Fusion Middleware 11gR1 ?FAQ??

    - by Hiroyuki Yoshino
    ??????FAQ????????????????? Oracle Technology Network (OTN)???????·??????·???????? Q. "Generic", "x86", "x86-64", ????????????????????????????????? A. ?????????????? Generic ????????·???????????????? 32????64???·??????????JDK/JVM????????? JDK/JVM???????????????????? x86 Supported System Configurations??????????????????????????????32???·???????????? x86-64 Supported System Configurations??????????????????????????????64???·???????????? ?????????? ("SPARC"??) Supported System Configurations????????????????????????????????????WebCenter for AIX?Portal, Forms, Reports and Discoverer for HP-UX PA-RISC???????? Q. SOA 11gR1 (11.1.1.1.0)??????????? 11gR1 (11.1.1.1.0)????????????????? A. ??????·????11gR1???????????????????????????????Oracle Support???????????????? Q. Oracle Fusion Middleware 11gR1???????????????????? A. Oracle Fusion Middleware 11gR1 ????????????????? Supported System Configurations?????????????? Q. Oracle Fusion Middleware 11gR1?????????????????????????????? A. Oracle Fusion Middleware?Oracle?????? Oracle Virtual Machine ????????????Oracle??????????????????????????????????????????????????? ???????? 

    Read the article

  • How to make the internal subwoofer work on an Asus G73JW?

    - by CodyLoco
    I have an Asus G73JW laptop which has an internal subwoofer built-in. Currently, the system detects the internal speakers as a 2.0 system (or I can change do 4.0 is the only other option). I found a bug report here: https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/673051 which discusses the bug and according to them a fix was sent upstream back at the end of 2010. I would have thought this would have made it into 12.04 but I guess not? I tried following the link given at the very bottom to install the latest ALSA drivers, here: https://wiki.ubuntu.com/Audio/InstallingLinuxAlsaDriverModules however I keep running into an error when trying to install: sudo apt-get install linux-alsa-driver-modules-$(uname -r) Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package linux-alsa-driver-modules-3.2.0-24-generic E: Couldn't find any package by regex 'linux-alsa-driver-modules-3.2.0-24-generic' I believe I have added the repository correctly: sudo add-apt-repository ppa:ubuntu-audio-dev/ppa [sudo] password for codyloco: You are about to add the following PPA to your system: This PPA will be used to provide testing versions of packages for supported Ubuntu releases. More info: https://launchpad.net/~ubuntu-audio-dev/+archive/ppa Press [ENTER] to continue or ctrl-c to cancel adding it Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /tmp/tmp.7apgZoNrqK --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver hkp://keyserver.ubuntu.com:80/ --recv 4E9F485BF943EF0EABA10B5BD225991A72B194E5 gpg: requesting key 72B194E5 from hkp server keyserver.ubuntu.com gpg: key 72B194E5: public key "Launchpad Ubuntu Audio Dev team PPA" imported gpg: Total number processed: 1 gpg: imported: 1 (RSA: 1) And I also ran an update as well (followed the instructions on the fix above). Any ideas?

    Read the article

  • What's wrong performing unit test against concrete implementation if your frameworks are not going to change?

    - by palm snow
    First a bit of background: We are re-architecting our product suite that was written 10 years ago and served its purpose. One thing that we cannot change is the database schema as we have 500+ client base using this system. Our db schema has over 150+ tables. We have decided on using Entity Framework 4.1 as DAL and still evaluating various frameworks for storing our business logic. I am investigation to bring unit testing into the mix but I also confused as to how far I need to go with setting up a full blown TDD environment. One aspect of setting up unit testing is by getting into implementing Repository, unit of work and mocking frameworks etc. This mean there will be cost and investment on the code-bloat associated with all these frameworks. I understand some of this could be auto-generated but when it comes to things like behaviors, that will be mostly hand written. Just to be clear, I am not questioning the important of unit testing your code. I am just not sure we need all its components (like repository, mocking etc.) when we are fairly certain of storage mechanism/framework (SQL Server/Entity Framework). All that code bloat with generic repositories make sense when you need a generic layers with ability to change this whenever you like however its very likely a YAGNI in our case. What we need is more of integration testing where we can unit-test our code with concrete repository objects and test data in database. In this scenario, just running integration test seem to be more beneficial in our case. Any thoughts if I am missing any thing here?

    Read the article

  • after BIOS splash, will not boot -- asks me to select an OS, but it just reboots

    - by user92040
    I'm running Linux Mint 13 MATE 64-bit. Everything has been working for several weeks. Yesterday, when I tried to boot up my computer, after the BIOS screen flashes I reach a screen with a black background that reads at the top: GNU GRUB version1.99-21ubuntu3.4 Then there is a box in which I can select from the following lines: Linux Mint 13 MATE 64-bit, 3.2.0-31-generic (/dev/sdb2) Linux Mint 13 MATE 64-bit, 3.2.0-31-generic (/dev/sdb2) -- recovery mode Previous Linux versions Memory test (memtest86+) Memory test (memtest86+, serial console 115200) At the bottom it reads: Use the ? and ? keys to select which entry is highlighed. Press enter to boot the selected OS, 'e' to edit the commands before booting or 'c' for a command-line. I have no idea why it started doing this and, worse, I have no idea how to get out of here. No matter which option I select, I can't get it to boot the OS. If I select either of the first two, it reboots to splash the BIOS and then I'm right back where I started. If I choose "Previous Linux versions" I get essentially the same screen with only two choices (which are the same as the first two choices listed above, Linux 13 MATE and the recovery mode). Again, choosing either one of those results in a reboot. If I try to run either of the memtest options, it reads: error: unknown command 'linux16', Press any key to continue... Then it brings me back to the same screen Can anyone help me please? Intel Core i5-2500 ASUS P8Z68-V LX Intel Motherboard G. Skill Ripjaws series F3-12800CL9D-8GBRL (4GB x2) Plextor 128GB M5S Series SSD

    Read the article

  • How can I go about learning to write a shader

    - by Donutz
    So here's the background: I'm writing a game, just for my own amusement and education really. I've already come to the conclusion that XNA was the way to go for graphics, I've bought a couple of books, I've gotten basic game graphics going, and that's great. Now I'm starting to get a little in-depth and I'm starting to need to do stuff not covered in my (beginner) books. In particular, I need to display a sprite using a mask. Actually, what I need to do is display a generic sprite with a different color for each player. After banging around on the web, it seems the way to go is to have a color texture (one for each player) which I display using the mask, then display the generic part of the sprite. This has to be done dynamically, i.e. at runtime because there are too many sprites to keep in memory if I try to generate all the permutations at startup. So, I need to use a shader. Fine. I've downloaded a sample shader program, and managed to hit it with a hammer until it does something close enough to what I want so that I know I'm on the right track. And here, we come to my problem... I have no friggin' clue what I'm doing. While there are a lot of samples and such about shaders, no one ever actually explains what's going on. For instance, I can't find any real docs on Tex2D. I feel like the guys in Zoolander poking at the computer. So, my question (yes, I have a question) -- where is a good URL or what is a good book to take me from dumskie to reasonably competent to write a basic shader?

    Read the article

  • No sound, can't adjust alsamixer volume

    - by user734613
    I have no sound on my ubuntu and I do not know why. I saw a lot of posts about that, I tried a lots of solutions that I found (especially this one) but it still does not work. I suspect alsamixer. I can't adjust the sound. http://img15.hostingpics.net/pics/447765Screenshotfrom20120621140430.png I tried to reinstall alsa mixer using this tutorial but it seems the package does not exist anymore. E: Unable to locate package linux-alsa-driver-modules-3.2.0-25-generic E: Couldn't find any package by regex 'linux-alsa-driver-modules-3.2.0-25-generic' Here are my configuration: cat /proc/driver/nvidia/version NVRM version: NVIDIA UNIX x86_64 Kernel Module 295.40 Thu Apr 5 21:37:00 PDT 2012 GCC version: gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) aplay -l List of PLAYBACK Hardware Devices ** card 0: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: NVidia [HDA NVidia], device 7: HDMI 1 [HDMI 1] Subdevices: 1/1 Subdevice #0: subdevice #0 grep eld_valid /proc/asound/NVidia/eld* /proc/asound/NVidia/eld#0.0:eld_valid 0 /proc/asound/NVidia/eld#0.1:eld_valid 0 Thanks in advance for your help.

    Read the article

  • How do I uninstall the TuxOnIce kernel in 12.04?

    - by Lluis
    I recently installed tuxonice on a Toshiba z830. I have ubuntu 12.04 (kernel was: 3.2.0-26) I wanted to be able to hibernate, which I consider to be a basic thing a OS should allow you to do. Well, it didn't work...but they already tell you it may not so I removed it. For doing all these I followed: Problem with Hibernation After uninstalling I switched off the laptop and after this I started to have several problems. The first one was that Cisco VPN didn't work anymore and then I realised that I could not even suspend my laptop. I found very strange that after removing tuxonice I still had this: /lib/modules/3.2.0-26-generic-tuxonice/ The VPN problem could be solved by just copying from my previous kernel: 3.2.0-26-generic/CiscoVPN/ into the tuxonice one. Not very elegant but works. Now, for the suspend problem (and the previous too) I can hold Shift when starting and select my old kernel and then suspend works again. In my opinion tuxonice was not correctly uninstalled as it left that kernel behind and worse: ubuntu uses it if I do not take action. I have these work arounds....and here is my question: how can I delete this tuxonice kernel safely? If you need more info please let me know.

    Read the article

  • How LINQ to Object statements work

    - by rajbk
    This post goes into detail as to now LINQ statements work when querying a collection of objects. This topic assumes you have an understanding of how generics, delegates, implicitly typed variables, lambda expressions, object/collection initializers, extension methods and the yield statement work. I would also recommend you read my previous two posts: Using Delegates in C# Part 1 Using Delegates in C# Part 2 We will start by writing some methods to filter a collection of data. Assume we have an Employee class like so: 1: public class Employee { 2: public int ID { get; set;} 3: public string FirstName { get; set;} 4: public string LastName {get; set;} 5: public string Country { get; set; } 6: } and a collection of employees like so: 1: var employees = new List<Employee> { 2: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 3: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 4: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 5: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" }, 6: }; Filtering We wish to  find all employees that have an even ID. We could start off by writing a method that takes in a list of employees and returns a filtered list of employees with an even ID. 1: static List<Employee> GetEmployeesWithEvenID(List<Employee> employees) { 2: var filteredEmployees = new List<Employee>(); 3: foreach (Employee emp in employees) { 4: if (emp.ID % 2 == 0) { 5: filteredEmployees.Add(emp); 6: } 7: } 8: return filteredEmployees; 9: } The method can be rewritten to return an IEnumerable<Employee> using the yield return keyword. 1: static IEnumerable<Employee> GetEmployeesWithEvenID(IEnumerable<Employee> employees) { 2: foreach (Employee emp in employees) { 3: if (emp.ID % 2 == 0) { 4: yield return emp; 5: } 6: } 7: } We put these together in a console application. 1: using System; 2: using System.Collections.Generic; 3: //No System.Linq 4:  5: public class Program 6: { 7: [STAThread] 8: static void Main(string[] args) 9: { 10: var employees = new List<Employee> { 11: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 12: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 13: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 14: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" }, 15: }; 16: var filteredEmployees = GetEmployeesWithEvenID(employees); 17:  18: foreach (Employee emp in filteredEmployees) { 19: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 20: emp.ID, emp.FirstName, emp.LastName, emp.Country); 21: } 22:  23: Console.ReadLine(); 24: } 25: 26: static IEnumerable<Employee> GetEmployeesWithEvenID(IEnumerable<Employee> employees) { 27: foreach (Employee emp in employees) { 28: if (emp.ID % 2 == 0) { 29: yield return emp; 30: } 31: } 32: } 33: } 34:  35: public class Employee { 36: public int ID { get; set;} 37: public string FirstName { get; set;} 38: public string LastName {get; set;} 39: public string Country { get; set; } 40: } Output: ID 2 First_Name Jim Last_Name Ashlock Country UK ID 4 First_Name Jill Last_Name Anderson Country AUS Our filtering method is too specific. Let us change it so that it is capable of doing different types of filtering and lets give our method the name Where ;-) We will add another parameter to our Where method. This additional parameter will be a delegate with the following declaration. public delegate bool Filter(Employee emp); The idea is that the delegate parameter in our Where method will point to a method that contains the logic to do our filtering thereby freeing our Where method from any dependency. The method is shown below: 1: static IEnumerable<Employee> Where(IEnumerable<Employee> employees, Filter filter) { 2: foreach (Employee emp in employees) { 3: if (filter(emp)) { 4: yield return emp; 5: } 6: } 7: } Making the change to our app, we create a new instance of the Filter delegate on line 14 with a target set to the method EmployeeHasEvenId. Running the code will produce the same output. 1: public delegate bool Filter(Employee emp); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: var employees = new List<Employee> { 9: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 10: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 11: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 12: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 13: }; 14: var filterDelegate = new Filter(EmployeeHasEvenId); 15: var filteredEmployees = Where(employees, filterDelegate); 16:  17: foreach (Employee emp in filteredEmployees) { 18: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 19: emp.ID, emp.FirstName, emp.LastName, emp.Country); 20: } 21: Console.ReadLine(); 22: } 23: 24: static bool EmployeeHasEvenId(Employee emp) { 25: return emp.ID % 2 == 0; 26: } 27: 28: static IEnumerable<Employee> Where(IEnumerable<Employee> employees, Filter filter) { 29: foreach (Employee emp in employees) { 30: if (filter(emp)) { 31: yield return emp; 32: } 33: } 34: } 35: } 36:  37: public class Employee { 38: public int ID { get; set;} 39: public string FirstName { get; set;} 40: public string LastName {get; set;} 41: public string Country { get; set; } 42: } Lets use lambda expressions to inline the contents of the EmployeeHasEvenId method in place of the method. The next code snippet shows this change (see line 15).  For brevity, the Employee class declaration has been skipped. 1: public delegate bool Filter(Employee emp); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: var employees = new List<Employee> { 9: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 10: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 11: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 12: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 13: }; 14: var filterDelegate = new Filter(EmployeeHasEvenId); 15: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 16:  17: foreach (Employee emp in filteredEmployees) { 18: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 19: emp.ID, emp.FirstName, emp.LastName, emp.Country); 20: } 21: Console.ReadLine(); 22: } 23: 24: static bool EmployeeHasEvenId(Employee emp) { 25: return emp.ID % 2 == 0; 26: } 27: 28: static IEnumerable<Employee> Where(IEnumerable<Employee> employees, Filter filter) { 29: foreach (Employee emp in employees) { 30: if (filter(emp)) { 31: yield return emp; 32: } 33: } 34: } 35: } 36:  The output displays the same two employees.  Our Where method is too restricted since it works with a collection of Employees only. Lets change it so that it works with any IEnumerable<T>. In addition, you may recall from my previous post,  that .NET 3.5 comes with a lot of predefined delegates including public delegate TResult Func<T, TResult>(T arg); We will get rid of our Filter delegate and use the one above instead. We apply these two changes to our code. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: var employees = new List<Employee> { 7: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 8: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 9: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 10: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 11: }; 12:  13: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 14:  15: foreach (Employee emp in filteredEmployees) { 16: Console.WriteLine("ID {0} First_Name {1} Last_Name {2} Country {3}", 17: emp.ID, emp.FirstName, emp.LastName, emp.Country); 18: } 19: Console.ReadLine(); 20: } 21: 22: static IEnumerable<T> Where<T>(IEnumerable<T> source, Func<T, bool> filter) { 23: foreach (var x in source) { 24: if (filter(x)) { 25: yield return x; 26: } 27: } 28: } 29: } We have successfully implemented a way to filter any IEnumerable<T> based on a  filter criteria. Projection Now lets enumerate on the items in the IEnumerable<Employee> we got from the Where method and copy them into a new IEnumerable<EmployeeFormatted>. The EmployeeFormatted class will only have a FullName and ID property. 1: public class EmployeeFormatted { 2: public int ID { get; set; } 3: public string FullName {get; set;} 4: } We could “project” our existing IEnumerable<Employee> into a new collection of IEnumerable<EmployeeFormatted> with the help of a new method. We will call this method Select ;-) 1: static IEnumerable<EmployeeFormatted> Select(IEnumerable<Employee> employees) { 2: foreach (var emp in employees) { 3: yield return new EmployeeFormatted { 4: ID = emp.ID, 5: FullName = emp.LastName + ", " + emp.FirstName 6: }; 7: } 8: } The changes are applied to our app. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: var employees = new List<Employee> { 7: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 8: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 9: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 10: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 11: }; 12:  13: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 14: var formattedEmployees = Select(filteredEmployees); 15:  16: foreach (EmployeeFormatted emp in formattedEmployees) { 17: Console.WriteLine("ID {0} Full_Name {1}", 18: emp.ID, emp.FullName); 19: } 20: Console.ReadLine(); 21: } 22:  23: static IEnumerable<T> Where<T>(IEnumerable<T> source, Func<T, bool> filter) { 24: foreach (var x in source) { 25: if (filter(x)) { 26: yield return x; 27: } 28: } 29: } 30: 31: static IEnumerable<EmployeeFormatted> Select(IEnumerable<Employee> employees) { 32: foreach (var emp in employees) { 33: yield return new EmployeeFormatted { 34: ID = emp.ID, 35: FullName = emp.LastName + ", " + emp.FirstName 36: }; 37: } 38: } 39: } 40:  41: public class Employee { 42: public int ID { get; set;} 43: public string FirstName { get; set;} 44: public string LastName {get; set;} 45: public string Country { get; set; } 46: } 47:  48: public class EmployeeFormatted { 49: public int ID { get; set; } 50: public string FullName {get; set;} 51: } Output: ID 2 Full_Name Ashlock, Jim ID 4 Full_Name Anderson, Jill We have successfully selected employees who have an even ID and then shaped our data with the help of the Select method so that the final result is an IEnumerable<EmployeeFormatted>.  Lets make our Select method more generic so that the user is given the freedom to shape what the output would look like. We can do this, like before, with lambda expressions. Our Select method is changed to accept a delegate as shown below. TSource will be the type of data that comes in and TResult will be the type the user chooses (shape of data) as returned from the selector delegate. 1:  2: static IEnumerable<TResult> Select<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, TResult> selector) { 3: foreach (var x in source) { 4: yield return selector(x); 5: } 6: } We see the new changes to our app. On line 15, we use lambda expression to specify the shape of the data. In this case the shape will be of type EmployeeFormatted. 1:  2: public class Program 3: { 4: [STAThread] 5: static void Main(string[] args) 6: { 7: var employees = new List<Employee> { 8: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 9: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 10: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 11: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 12: }; 13:  14: var filteredEmployees = Where(employees, emp => emp.ID % 2 == 0); 15: var formattedEmployees = Select(filteredEmployees, (emp) => 16: new EmployeeFormatted { 17: ID = emp.ID, 18: FullName = emp.LastName + ", " + emp.FirstName 19: }); 20:  21: foreach (EmployeeFormatted emp in formattedEmployees) { 22: Console.WriteLine("ID {0} Full_Name {1}", 23: emp.ID, emp.FullName); 24: } 25: Console.ReadLine(); 26: } 27: 28: static IEnumerable<T> Where<T>(IEnumerable<T> source, Func<T, bool> filter) { 29: foreach (var x in source) { 30: if (filter(x)) { 31: yield return x; 32: } 33: } 34: } 35: 36: static IEnumerable<TResult> Select<TSource, TResult>(IEnumerable<TSource> source, Func<TSource, TResult> selector) { 37: foreach (var x in source) { 38: yield return selector(x); 39: } 40: } 41: } The code outputs the same result as before. On line 14 we filter our data and on line 15 we project our data. What if we wanted to be more expressive and concise? We could combine both line 14 and 15 into one line as shown below. Assuming you had to perform several operations like this on our collection, you would end up with some very unreadable code! 1: var formattedEmployees = Select(Where(employees, emp => emp.ID % 2 == 0), (emp) => 2: new EmployeeFormatted { 3: ID = emp.ID, 4: FullName = emp.LastName + ", " + emp.FirstName 5: }); A cleaner way to write this would be to give the appearance that the Select and Where methods were part of the IEnumerable<T>. This is exactly what extension methods give us. Extension methods have to be defined in a static class. Let us make the Select and Where extension methods on IEnumerable<T> 1: public static class MyExtensionMethods { 2: static IEnumerable<T> Where<T>(this IEnumerable<T> source, Func<T, bool> filter) { 3: foreach (var x in source) { 4: if (filter(x)) { 5: yield return x; 6: } 7: } 8: } 9: 10: static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) { 11: foreach (var x in source) { 12: yield return selector(x); 13: } 14: } 15: } The creation of the extension method makes the syntax much cleaner as shown below. We can write as many extension methods as we want and keep on chaining them using this technique. 1: var formattedEmployees = employees 2: .Where(emp => emp.ID % 2 == 0) 3: .Select (emp => new EmployeeFormatted { ID = emp.ID, FullName = emp.LastName + ", " + emp.FirstName }); Making these changes and running our code produces the same result. 1: using System; 2: using System.Collections.Generic; 3:  4: public class Program 5: { 6: [STAThread] 7: static void Main(string[] args) 8: { 9: var employees = new List<Employee> { 10: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 11: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 12: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 13: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 14: }; 15:  16: var formattedEmployees = employees 17: .Where(emp => emp.ID % 2 == 0) 18: .Select (emp => 19: new EmployeeFormatted { 20: ID = emp.ID, 21: FullName = emp.LastName + ", " + emp.FirstName 22: } 23: ); 24:  25: foreach (EmployeeFormatted emp in formattedEmployees) { 26: Console.WriteLine("ID {0} Full_Name {1}", 27: emp.ID, emp.FullName); 28: } 29: Console.ReadLine(); 30: } 31: } 32:  33: public static class MyExtensionMethods { 34: static IEnumerable<T> Where<T>(this IEnumerable<T> source, Func<T, bool> filter) { 35: foreach (var x in source) { 36: if (filter(x)) { 37: yield return x; 38: } 39: } 40: } 41: 42: static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) { 43: foreach (var x in source) { 44: yield return selector(x); 45: } 46: } 47: } 48:  49: public class Employee { 50: public int ID { get; set;} 51: public string FirstName { get; set;} 52: public string LastName {get; set;} 53: public string Country { get; set; } 54: } 55:  56: public class EmployeeFormatted { 57: public int ID { get; set; } 58: public string FullName {get; set;} 59: } Let’s change our code to return a collection of anonymous types and get rid of the EmployeeFormatted type. We see that the code produces the same output. 1: using System; 2: using System.Collections.Generic; 3:  4: public class Program 5: { 6: [STAThread] 7: static void Main(string[] args) 8: { 9: var employees = new List<Employee> { 10: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 11: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 12: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 13: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 14: }; 15:  16: var formattedEmployees = employees 17: .Where(emp => emp.ID % 2 == 0) 18: .Select (emp => 19: new { 20: ID = emp.ID, 21: FullName = emp.LastName + ", " + emp.FirstName 22: } 23: ); 24:  25: foreach (var emp in formattedEmployees) { 26: Console.WriteLine("ID {0} Full_Name {1}", 27: emp.ID, emp.FullName); 28: } 29: Console.ReadLine(); 30: } 31: } 32:  33: public static class MyExtensionMethods { 34: public static IEnumerable<T> Where<T>(this IEnumerable<T> source, Func<T, bool> filter) { 35: foreach (var x in source) { 36: if (filter(x)) { 37: yield return x; 38: } 39: } 40: } 41: 42: public static IEnumerable<TResult> Select<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> selector) { 43: foreach (var x in source) { 44: yield return selector(x); 45: } 46: } 47: } 48:  49: public class Employee { 50: public int ID { get; set;} 51: public string FirstName { get; set;} 52: public string LastName {get; set;} 53: public string Country { get; set; } 54: } To be more expressive, C# allows us to write our extension method calls as a query expression. Line 16 can be rewritten a query expression like so: 1: var formattedEmployees = from emp in employees 2: where emp.ID % 2 == 0 3: select new { 4: ID = emp.ID, 5: FullName = emp.LastName + ", " + emp.FirstName 6: }; When the compiler encounters an expression like the above, it simply rewrites it as calls to our extension methods.  So far we have been using our extension methods. The System.Linq namespace contains several extension methods for objects that implement the IEnumerable<T>. You can see a listing of these methods in the Enumerable class in the System.Linq namespace. Let’s get rid of our extension methods (which I purposefully wrote to be of the same signature as the ones in the Enumerable class) and use the ones provided in the Enumerable class. Our final code is shown below: 1: using System; 2: using System.Collections.Generic; 3: using System.Linq; //Added 4:  5: public class Program 6: { 7: [STAThread] 8: static void Main(string[] args) 9: { 10: var employees = new List<Employee> { 11: new Employee { ID = 1, FirstName = "John", LastName = "Wright", Country = "USA" }, 12: new Employee { ID = 2, FirstName = "Jim", LastName = "Ashlock", Country = "UK" }, 13: new Employee { ID = 3, FirstName = "Jane", LastName = "Jackson", Country = "CHE" }, 14: new Employee { ID = 4, FirstName = "Jill", LastName = "Anderson", Country = "AUS" } 15: }; 16:  17: var formattedEmployees = from emp in employees 18: where emp.ID % 2 == 0 19: select new { 20: ID = emp.ID, 21: FullName = emp.LastName + ", " + emp.FirstName 22: }; 23:  24: foreach (var emp in formattedEmployees) { 25: Console.WriteLine("ID {0} Full_Name {1}", 26: emp.ID, emp.FullName); 27: } 28: Console.ReadLine(); 29: } 30: } 31:  32: public class Employee { 33: public int ID { get; set;} 34: public string FirstName { get; set;} 35: public string LastName {get; set;} 36: public string Country { get; set; } 37: } 38:  39: public class EmployeeFormatted { 40: public int ID { get; set; } 41: public string FullName {get; set;} 42: } This post has shown you a basic overview of LINQ to Objects work by showning you how an expression is converted to a sequence of calls to extension methods when working directly with objects. It gets more interesting when working with LINQ to SQL where an expression tree is constructed – an in memory data representation of the expression. The C# compiler compiles these expressions into code that builds an expression tree at runtime. The provider can then traverse the expression tree and generate the appropriate SQL query. You can read more about expression trees in this MSDN article.

    Read the article

  • Introduction to the ASP.NET Web API

    - by Stephen.Walther
    I am a huge fan of Ajax. If you want to create a great experience for the users of your website – regardless of whether you are building an ASP.NET MVC or an ASP.NET Web Forms site — then you need to use Ajax. Otherwise, you are just being cruel to your customers. We use Ajax extensively in several of the ASP.NET applications that my company, Superexpert.com, builds. We expose data from the server as JSON and use jQuery to retrieve and update that data from the browser. One challenge, when building an ASP.NET website, is deciding on which technology to use to expose JSON data from the server. For example, how do you expose a list of products from the server as JSON so you can retrieve the list of products with jQuery? You have a number of options (too many options) including ASMX Web services, WCF Web Services, ASHX Generic Handlers, WCF Data Services, and MVC controller actions. Fortunately, the world has just been simplified. With the release of ASP.NET 4 Beta, Microsoft has introduced a new technology for exposing JSON from the server named the ASP.NET Web API. You can use the ASP.NET Web API with both ASP.NET MVC and ASP.NET Web Forms applications. The goal of this blog post is to provide you with a brief overview of the features of the new ASP.NET Web API. You learn how to use the ASP.NET Web API to retrieve, insert, update, and delete database records with jQuery. We also discuss how you can perform form validation when using the Web API and use OData when using the Web API. Creating an ASP.NET Web API Controller The ASP.NET Web API exposes JSON data through a new type of controller called an API controller. You can add an API controller to an existing ASP.NET MVC 4 project through the standard Add Controller dialog box. Right-click your Controllers folder and select Add, Controller. In the dialog box, name your controller MovieController and select the Empty API controller template: A brand new API controller looks like this: using System; using System.Collections.Generic; using System.Linq; using System.Net.Http; using System.Web.Http; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { } } An API controller, unlike a standard MVC controller, derives from the base ApiController class instead of the base Controller class. Using jQuery to Retrieve, Insert, Update, and Delete Data Let’s create an Ajaxified Movie Database application. We’ll retrieve, insert, update, and delete movies using jQuery with the MovieController which we just created. Our Movie model class looks like this: namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } public string Title { get; set; } public string Director { get; set; } } } Our application will consist of a single HTML page named Movies.html. We’ll place all of our jQuery code in the Movies.html page. Getting a Single Record with the ASP.NET Web API To support retrieving a single movie from the server, we need to add a Get method to our API controller: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public Movie GetMovie(int id) { // Return movie by id if (id == 1) { return new Movie { Id = 1, Title = "Star Wars", Director = "Lucas" }; } // Otherwise, movie was not found throw new HttpResponseException(HttpStatusCode.NotFound); } } } In the code above, the GetMovie() method accepts the Id of a movie. If the Id has the value 1 then the method returns the movie Star Wars. Otherwise, the method throws an exception and returns 404 Not Found HTTP status code. After building your project, you can invoke the MovieController.GetMovie() method by entering the following URL in your web browser address bar: http://localhost:[port]/api/movie/1 (You’ll need to enter the correct randomly generated port). In the URL api/movie/1, the first “api” segment indicates that this is a Web API route. The “movie” segment indicates that the MovieController should be invoked. You do not specify the name of the action. Instead, the HTTP method used to make the request – GET, POST, PUT, DELETE — is used to identify the action to invoke. The ASP.NET Web API uses different routing conventions than normal ASP.NET MVC controllers. When you make an HTTP GET request then any API controller method with a name that starts with “GET” is invoked. So, we could have called our API controller action GetPopcorn() instead of GetMovie() and it would still be invoked by the URL api/movie/1. The default route for the Web API is defined in the Global.asax file and it looks like this: routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); We can invoke our GetMovie() controller action with the jQuery code in the following HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Get Movie</title> </head> <body> <div> Title: <span id="title"></span> </div> <div> Director: <span id="director"></span> </div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> getMovie(1, function (movie) { $("#title").html(movie.Title); $("#director").html(movie.Director); }); function getMovie(id, callback) { $.ajax({ url: "/api/Movie", data: { id: id }, type: "GET", contentType: "application/json;charset=utf-8", statusCode: { 200: function (movie) { callback(movie); }, 404: function () { alert("Not Found!"); } } }); } </script> </body> </html> In the code above, the jQuery $.ajax() method is used to invoke the GetMovie() method. Notice that the Ajax call handles two HTTP response codes. When the GetMove() method successfully returns a movie, the method returns a 200 status code. In that case, the details of the movie are displayed in the HTML page. Otherwise, if the movie is not found, the GetMovie() method returns a 404 status code. In that case, the page simply displays an alert box indicating that the movie was not found (hopefully, you would implement something more graceful in an actual application). You can use your browser’s Developer Tools to see what is going on in the background when you open the HTML page (hit F12 in the most recent version of most browsers). For example, you can use the Network tab in Google Chrome to see the Ajax request which invokes the GetMovie() method: Getting a Set of Records with the ASP.NET Web API Let’s modify our Movie API controller so that it returns a collection of movies. The following Movie controller has a new ListMovies() method which returns a (hard-coded) collection of movies: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public IEnumerable<Movie> ListMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=1, Title="King Kong", Director="Jackson"}, new Movie {Id=1, Title="Memento", Director="Nolan"} }; } } } Because we named our action ListMovies(), the default Web API route will never match it. Therefore, we need to add the following custom route to our Global.asax file (at the top of the RegisterRoutes() method): routes.MapHttpRoute( name: "ActionApi", routeTemplate: "api/{controller}/{action}/{id}", defaults: new { id = RouteParameter.Optional } ); This route enables us to invoke the ListMovies() method with the URL /api/movie/listmovies. Now that we have exposed our collection of movies from the server, we can retrieve and display the list of movies using jQuery in our HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>List Movies</title> </head> <body> <div id="movies"></div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> listMovies(function (movies) { var strMovies=""; $.each(movies, function (index, movie) { strMovies += "<div>" + movie.Title + "</div>"; }); $("#movies").html(strMovies); }); function listMovies(callback) { $.ajax({ url: "/api/Movie/ListMovies", data: {}, type: "GET", contentType: "application/json;charset=utf-8", }).then(function(movies){ callback(movies); }); } </script> </body> </html>     Inserting a Record with the ASP.NET Web API Now let’s modify our Movie API controller so it supports creating new records: public HttpResponseMessage<Movie> PostMovie(Movie movieToCreate) { // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } The PostMovie() method in the code above accepts a movieToCreate parameter. We don’t actually store the new movie anywhere. In real life, you will want to call a service method to store the new movie in a database. When you create a new resource, such as a new movie, you should return the location of the new resource. In the code above, the URL where the new movie can be retrieved is assigned to the Location header returned in the PostMovie() response. Because the name of our method starts with “Post”, we don’t need to create a custom route. The PostMovie() method can be invoked with the URL /Movie/PostMovie – just as long as the method is invoked within the context of a HTTP POST request. The following HTML page invokes the PostMovie() method. <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "Jackson" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }); function createMovie(movieToCreate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); } </script> </body> </html> This page creates a new movie (the Hobbit) by calling the createMovie() method. The page simply displays the Id of the new movie: The HTTP Post operation is performed with the following call to the jQuery $.ajax() method: $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); Notice that the type of Ajax request is a POST request. This is required to match the PostMovie() method. Notice, furthermore, that the new movie is converted into JSON using JSON.stringify(). The JSON.stringify() method takes a JavaScript object and converts it into a JSON string. Finally, notice that success is represented with a 201 status code. The HttpStatusCode.Created value returned from the PostMovie() method returns a 201 status code. Updating a Record with the ASP.NET Web API Here’s how we can modify the Movie API controller to support updating an existing record. In this case, we need to create a PUT method to handle an HTTP PUT request: public void PutMovie(Movie movieToUpdate) { if (movieToUpdate.Id == 1) { // Update the movie in the database return; } // If you can't find the movie to update throw new HttpResponseException(HttpStatusCode.NotFound); } Unlike our PostMovie() method, the PutMovie() method does not return a result. The action either updates the database or, if the movie cannot be found, returns an HTTP Status code of 404. The following HTML page illustrates how you can invoke the PutMovie() method: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Put Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToUpdate = { id: 1, title: "The Hobbit", director: "Jackson" }; updateMovie(movieToUpdate, function () { alert("Movie updated!"); }); function updateMovie(movieToUpdate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToUpdate), type: "PUT", contentType: "application/json;charset=utf-8", statusCode: { 200: function () { callback(); }, 404: function () { alert("Movie not found!"); } } }); } </script> </body> </html> Deleting a Record with the ASP.NET Web API Here’s the code for deleting a movie: public HttpResponseMessage DeleteMovie(int id) { // Delete the movie from the database // Return status code return new HttpResponseMessage(HttpStatusCode.NoContent); } This method simply deletes the movie (well, not really, but pretend that it does) and returns a No Content status code (204). The following page illustrates how you can invoke the DeleteMovie() action: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Delete Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> deleteMovie(1, function () { alert("Movie deleted!"); }); function deleteMovie(id, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify({id:id}), type: "DELETE", contentType: "application/json;charset=utf-8", statusCode: { 204: function () { callback(); } } }); } </script> </body> </html> Performing Validation How do you perform form validation when using the ASP.NET Web API? Because validation in ASP.NET MVC is driven by the Default Model Binder, and because the Web API uses the Default Model Binder, you get validation for free. Let’s modify our Movie class so it includes some of the standard validation attributes: using System.ComponentModel.DataAnnotations; namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } [Required(ErrorMessage="Title is required!")] [StringLength(5, ErrorMessage="Title cannot be more than 5 characters!")] public string Title { get; set; } [Required(ErrorMessage="Director is required!")] public string Director { get; set; } } } In the code above, the Required validation attribute is used to make both the Title and Director properties required. The StringLength attribute is used to require the length of the movie title to be no more than 5 characters. Now let’s modify our PostMovie() action to validate a movie before adding the movie to the database: public HttpResponseMessage PostMovie(Movie movieToCreate) { // Validate movie if (!ModelState.IsValid) { var errors = new JsonArray(); foreach (var prop in ModelState.Values) { if (prop.Errors.Any()) { errors.Add(prop.Errors.First().ErrorMessage); } } return new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } If ModelState.IsValid has the value false then the errors in model state are copied to a new JSON array. Each property – such as the Title and Director property — can have multiple errors. In the code above, only the first error message is copied over. The JSON array is returned with a Bad Request status code (400 status code). The following HTML page illustrates how you can invoke our modified PostMovie() action and display any error messages: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }, function (errors) { var strErrors = ""; $.each(errors, function(index, err) { strErrors += "*" + err + "\n"; }); alert(strErrors); } ); function createMovie(movieToCreate, success, fail) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToCreate), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { success(newMovie); }, 400: function (xhr) { var errors = JSON.parse(xhr.responseText); fail(errors); } } }); } </script> </body> </html> The createMovie() function performs an Ajax request and handles either a 201 or a 400 status code from the response. If a 201 status code is returned then there were no validation errors and the new movie was created. If, on the other hand, a 400 status code is returned then there was a validation error. The validation errors are retrieved from the XmlHttpRequest responseText property. The error messages are displayed in an alert: (Please don’t use JavaScript alert dialogs to display validation errors, I just did it this way out of pure laziness) This validation code in our PostMovie() method is pretty generic. There is nothing specific about this code to the PostMovie() method. In the following video, Jon Galloway demonstrates how to create a global Validation filter which can be used with any API controller action: http://www.asp.net/web-api/overview/web-api-routing-and-actions/video-custom-validation His validation filter looks like this: using System.Json; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http.Controllers; using System.Web.Http.Filters; namespace MyWebAPIApp.Filters { public class ValidationActionFilter:ActionFilterAttribute { public override void OnActionExecuting(HttpActionContext actionContext) { var modelState = actionContext.ModelState; if (!modelState.IsValid) { dynamic errors = new JsonObject(); foreach (var key in modelState.Keys) { var state = modelState[key]; if (state.Errors.Any()) { errors[key] = state.Errors.First().ErrorMessage; } } actionContext.Response = new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } } } } And you can register the validation filter in the Application_Start() method in the Global.asax file like this: GlobalConfiguration.Configuration.Filters.Add(new ValidationActionFilter()); After you register the Validation filter, validation error messages are returned from any API controller action method automatically when validation fails. You don’t need to add any special logic to any of your API controller actions to take advantage of the filter. Querying using OData The OData protocol is an open protocol created by Microsoft which enables you to perform queries over the web. The official website for OData is located here: http://odata.org For example, here are some of the query options which you can use with OData: · $orderby – Enables you to retrieve results in a certain order. · $top – Enables you to retrieve a certain number of results. · $skip – Enables you to skip over a certain number of results (use with $top for paging). · $filter – Enables you to filter the results returned. The ASP.NET Web API supports a subset of the OData protocol. You can use all of the query options listed above when interacting with an API controller. The only requirement is that the API controller action returns its data as IQueryable. For example, the following Movie controller has an action named GetMovies() which returns an IQueryable of movies: public IQueryable<Movie> GetMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=2, Title="King Kong", Director="Jackson"}, new Movie {Id=3, Title="Willow", Director="Lucas"}, new Movie {Id=4, Title="Shrek", Director="Smith"}, new Movie {Id=5, Title="Memento", Director="Nolan"} }.AsQueryable(); } If you enter the following URL in your browser: /api/movie?$top=2&$orderby=Title Then you will limit the movies returned to the top 2 in order of the movie Title. You will get the following results: By using the $top option in combination with the $skip option, you can enable client-side paging. For example, you can use $top and $skip to page through thousands of products, 10 products at a time. The $filter query option is very powerful. You can use this option to filter the results from a query. Here are some examples: Return every movie directed by Lucas: /api/movie?$filter=Director eq ‘Lucas’ Return every movie which has a title which starts with ‘S’: /api/movie?$filter=startswith(Title,’S') Return every movie which has an Id greater than 2: /api/movie?$filter=Id gt 2 The complete documentation for the $filter option is located here: http://www.odata.org/developers/protocols/uri-conventions#FilterSystemQueryOption Summary The goal of this blog entry was to provide you with an overview of the new ASP.NET Web API introduced with the Beta release of ASP.NET 4. In this post, I discussed how you can retrieve, insert, update, and delete data by using jQuery with the Web API. I also discussed how you can use the standard validation attributes with the Web API. You learned how to return validation error messages to the client and display the error messages using jQuery. Finally, we briefly discussed how the ASP.NET Web API supports the OData protocol. For example, you learned how to filter records returned from an API controller action by using the $filter query option. I’m excited about the new Web API. This is a feature which I expect to use with almost every ASP.NET application which I build in the future.

    Read the article

< Previous Page | 58 59 60 61 62 63 64 65 66 67 68 69  | Next Page >