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  • What is the meaning of ": base" in the costructor definition ?

    - by DotNetBeginner
    What is the meaning of ": base" in the costructor of following class(MyClass) ? Please explain the concept behind constructor definition given below for class MyClass. public class MyClass: WorkerThread { public MyClass(object data): base(data) { // some code } } public abstract class WorkerThread { private object ThreadData; private Thread thisThread; public WorkerThread(object data) { this.ThreadData = data; } public WorkerThread() { ThreadData = null; } }

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  • XSD: xs:sequence & xs:choice combination for xs:extension elements of a common base type?

    - by bguiz
    Hi, My question is about defining an XML schema that will validate the following XML: <rules> <other>...</other> <bool>...</bool> <other>...</other> <string>...</string> <other>...</other> </rules> The order of the child nodes does not matter. The cardinality of the child nodes is 0..unbounded. All the child elements of the rules node have a common base type, rule, like so: <xs:complexType name="booleanRule"> <xs:complexContent> <xs:extension base="rule"> ... </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="stringFilterRule"> <xs:complexContent> <xs:extension base="filterRule"> ... </xs:extension> </xs:complexContent> </xs:complexType> My current (feeble) attempt at defining the schema for the rules node is below. However, Can I nest xs:choice within xs:sequence? If, where do I specify the maxOccurs="unbounded" attribute? Is there a better way to do this, such as an xs:sequence which specifies only the base type of its child elements? <xs:element name="rules"> <xs:complexType> <xs:sequence> <xs:choice> <xs:element name="bool" type="booleanRule" /> <xs:element name="string" type="stringRule" /> <xs:element name="other" type="someOtherRule" /> </xs:choice> </xs:sequence> </xs:complexType> </xs:element>

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  • How do I get the action name from a base controller?

    - by griegs
    Hi, I'd like to implement a base controller on one of my controllers. Within that base controller, I'd like to be able to get the current executing ActionResult name. How would I go about doing this? public class HomeController : ControllerBase { public ActionResult Index() { And; public class ControllerBase : Controller { public ControllerBase() { //method which will get the executing ActionResult } }

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  • Windows Server 2008 - one MAC Address, assign multiple external IP's to VirtualBoxes running as guests on host

    - by Sise
    Couldn't find any help @ google or here. The scenario: Windows Server 2008 Std x64 on i7-975, 12 GB RAM. The server is running in a data centre. One hardware NIC - RealTek PCIe GBE - one MAC Address. The data centre provides us 4 static external IP's. The first is assigned to the host by default of course. I have ordered all 4 IP's, the data centre can assign the available IP's to the physical MAC address of the given NIC only. This means one NIC, one MAC Address, 4 IP's. Everything works fine so far. Now, what I would like to have: Installed VirtualBox with 1-3 guests running, each gets it's own external IP assigned. Each of it should be an standalone Win Server 2008. It looks like the easiest way would be to put the guests into an virtual subnet and routing all data coming to the 2nd till 4th external IP through to this guests using there subnet IP's. I have been through the VirtualBox User Manuel regarding networking. What's not working: I can't use bridged networking without anything else, because the IP's are assigned to the one MAC address only. I can't use NAT networking because it does not allow access from outside or the host to the guest. I do not wanna use port forwarding. Host-only networking itself would not allow internet access, by sharing the default internet connection of the host, internet is granted from the guest to the outside but not from outside or the host to the guest. InternalNetworking is not really an option here. What I have tried is to create an additional MS Loopback adapter for a routed subnet, where the Vbox guests are in, now the idea was to NAT the internet connection to the loopback 'subnet'. But I can't ping the gateway from the guests. By using route command in the command shell or RRAS (static route, NAT) I didn't get there as well. Solutions like the following do work for the one way, but not for the way back: For your situation, it might be best to use the Host-Only adapter for ICS. Go to the preferences of VB itself and select network. There you can change the configuration for the interface. Set the IP address to 192.168.0.1, netmask 255.255.255.0. Disable the DHCP server if it isn't already and that's it. Now the Guest should get an IP from Windows itself and be able to get onto the internet, while you can also access the Host. Slowly I'm pretty stucked with this topic. There is a possibility I've just overlooked something or just didn't getting it by trying, especially using RRAS, but it's kinda hard to find useful howto's or something in the web. Thanks in advance! Best regards, Simon

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  • How to configure Transparent IP Address Sharing (TAS) on a Mediatrix 4102 with DGW 2.0 firmware?

    - by Pascal Bourque
    I am making the switch to VoIP. I chose voip.ms as my service provider and Mediatrix 4102 as my ATA. One reason why I chose the Mediatrix over other popular consumer ATAs is that it's supposed to be easy to place it in front of the router, so it can give priority to its own upstream traffic over the home network's upstream traffic. This is supposed to work transparently, with the ATA and router sharing the same public IP address (the one obtained from the modem). They call this feaure Transparent IP Address Sharing, or TAS. Their promotional brochure describes it like this: The Mediatrix 4102 also uses its innovative TAS (Transparent IP Address Sharing) technology and an embedded PPPoE client to allow the PC (or router) connected to the second Ethernet port to have the same public IP address, eliminating the need for private IP addresses or address translations. I am interested by this feature because my router, an Apple Time Capsule, doesn't support QoS and cannot give priority to the voice packets if the ATA is behind the router. However, after hours of searching the web, reading the documentation, and good ol' trial and error, I haven't been able to configure the Mediatrix to run in this mode. Then I found a version of the manual that looks like it was for a previous version of the firmware (SIP), where there is an entire section dedicated to configuring TAS (starting at page 209). But my Mediatrix comes with the DGW 2.0 firmware, whose documentation does not mention TAS at all. So I tried to follow the TAS setup instructions from the SIP documentation and apply them to my DGW firmware, using the Variable Mapping Between SIP v5.0 and DGW v2.0 document as a reference, but no success. Some required SIP variables don't have an equivalent in DGW. So it looks like the DGW firmware does not support TAS at all, or if it does they are not doing anything to help us set it up. So right now, the Mediatrix is behind the router and VoIP works perfectly except when my upstream bandwidth is saturated. My questions are: Is downgrading to SIP firmware the only way to have my Mediatrix 4102 run in TAS mode? If not, anybody knows how to setup TAS on the DGW firmware? Is TAS mode the only way to give priority to the voice packets if I want to keep my current router (Apple Time Capsule)? Thanks!

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  • How to configure Transparent IP Address Sharing (TAS) on a Mediatrix 4102 with DGW 2.0 firmware?

    - by Pascal Bourque
    I am making the switch to VoIP. I chose voip.ms as my service provider and Mediatrix 4102 as my ATA. One reason why I chose the Mediatrix over other popular consumer ATAs is that it's supposed to be easy to place it in front of the router, so it can give priority to its own upstream traffic over the home network's upstream traffic. This is supposed to work transparently, with the ATA and router sharing the same public IP address (the one obtained from the modem). They call this feaure Transparent IP Address Sharing, or TAS. Their promotional brochure describes it like this: The Mediatrix 4102 also uses its innovative TAS (Transparent IP Address Sharing) technology and an embedded PPPoE client to allow the PC (or router) connected to the second Ethernet port to have the same public IP address, eliminating the need for private IP addresses or address translations. I am interested by this feature because my router, an Apple Time Capsule, doesn't support QoS and cannot give priority to the voice packets if the ATA is behind the router. However, after hours of searching the web, reading the documentation, and good ol' trial and error, I haven't been able to configure the Mediatrix to run in this mode. Then I found a version of the manual that looks like it was for a previous version of the firmware (SIP), where there is an entire section dedicated to configuring TAS (starting at page 209). But my Mediatrix comes with the DGW 2.0 firmware, whose documentation does not mention TAS at all. So I tried to follow the TAS setup instructions from the SIP documentation and apply them to my DGW firmware, using the Variable Mapping Between SIP v5.0 and DGW v2.0 document as a reference, but no success. Some required SIP variables don't have an equivalent in DGW. So it looks like the DGW firmware does not support TAS at all, or if it does they are not doing anything to help us set it up. So right now, the Mediatrix is behind the router and VoIP works perfectly except when my upstream bandwidth is saturated. My questions are: Is downgrading to SIP firmware the only way to have my Mediatrix 4102 run in TAS mode? If not, anybody knows how to setup TAS on the DGW firmware? Is TAS mode the only way to give priority to the voice packets if I want to keep my current router (Apple Time Capsule)? Thanks!

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  • Windows Server 2008 - one MAC Address, assign multiple external IP's to VirtualBoxes running as guests on host

    - by Sise
    Couldn't find any help @ google or here. The scenario: Windows Server 2008 Std x64 on i7-975, 12 GB RAM. The server is running in a data centre. One hardware NIC - RealTek PCIe GBE - one MAC Address. The data centre provides us 4 static external IP's. The first is assigned to the host by default of course. I have ordered all 4 IP's, the data centre can assign the available IP's to the physical MAC address of the given NIC only. This means one NIC, one MAC Address, 4 IP's. Everything works fine so far. Now, what I would like to have: Installed VirtualBox with 1-3 guests running, each gets it's own external IP assigned. Each of it should be an standalone Win Server 2008. It looks like the easiest way would be to put the guests into an virtual subnet and routing all data coming to the 2nd till 4th external IP through to this guests using there subnet IP's. I have been through the VirtualBox User Manuel regarding networking. What's not working: I can't use bridged networking without anything else, because the IP's are assigned to the one MAC address only. I can't use NAT networking because it does not allow access from outside or the host to the guest. I do not wanna use port forwarding. Host-only networking itself would not allow internet access, by sharing the default internet connection of the host, internet is granted from the guest to the outside but not from outside or the host to the guest. InternalNetworking is not really an option here. What I have tried is to create an additional MS Loopback adapter for a routed subnet, where the Vbox guests are in, now the idea was to NAT the internet connection to the loopback 'subnet'. But I can't ping the gateway from the guests. By using route command in the command shell or RRAS (static route, NAT) I didn't get there as well. Solutions like the following do work for the one way, but not for the way back: For your situation, it might be best to use the Host-Only adapter for ICS. Go to the preferences of VB itself and select network. There you can change the configuration for the interface. Set the IP address to 192.168.0.1, netmask 255.255.255.0. Disable the DHCP server if it isn't already and that's it. Now the Guest should get an IP from Windows itself and be able to get onto the internet, while you can also access the Host. Slowly I'm pretty stucked with this topic. There is a possibility I've just overlooked something or just didn't getting it by trying, especially using RRAS, but it's kinda hard to find useful howto's or something in the web. Thanks in advance! Best regards, Simon

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  • asp.net Can I force every page to inherit from a base page? Also should some of this logic be in my master page?

    - by Bex
    Hi! I have a web app that has a base page. Each page needs to inherit from this base page as it contains properties they all need as well as dealing with the login rights. My base page has some properties, eg: IsRole1, IsRole2, currentUserID, Role1Allowed, Role2Allowed. On the init of each page I set the properties "Role1Allowed" and "Role2Allowed" Private Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init Role1Allowed = True Role2Allowed= False End Sub The basepage then decides if the user needs redirecting. 'Sample code so not exactly what is going to be, bug gives the idea Protected Overridable Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) If Role1Allowed And Not Role1 Then 'Redirect somewhere End If End Sub The page then must override this pageload if they need anything else in it, but making sure they call the base pageload first. Protected Overrides Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load MyBase.Page_Load(sender, e) If Not IsPostBack Then BindGrid() End If End Sub The other properties (IsRole1, IsRole, currentUserID) are also accessible by the page so it can be decided if certain things need doing based on the user. (I hope this makes sense) Ok so I have 2 questions Should this functionality be in the base page or should it somehow be in the master, and if so how would I get access to all the properties if it was? As there are multiple people working on this project and creating pages some are forgetting to inherit from this basepage, or call the base pageload when overriding it. Is there any way to force them to do this? Thanks for any help. bex

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  • Why does the VS2005 debugger not report "base." values properly? (was "Why is this if statement fail

    - by Rawling
    I'm working on an existing class that is two steps derived from System.Windows.Forms.Combo box. The class overrides the Text property thus: public override string Text { get { return this.AccessibilityObject.Value; } set { if (base.Text != value) { base.Text = value; } } } The reason given for that "get" is this MS bug: http://support.microsoft.com/kb/814346 However, I'm more interested in the fact that the "if" doesn't work. There are times where "base.Text != value" is true and yet pressing F10 steps straight to the closing } of the "set" and the Text property is not changed. I've seen this both by just checking values in the debugger, and putting a conditional breakpoint on that only breaks when the "if" statement's predicate is true. How on earth can "if" go wrong? The class between this and ComboBox doesn't touch the Text property. The bug above shouldn't really be affecting anything - it says it's fixed in VS2005. Is the debugger showing different values than the program itself sees? Update I think I've found what is happening here. The debugger is reporting value incorrectly (including evaluating conditional breakpoints incorrectly). To see this, try the following pair of classes: class MyBase { virtual public string Text { get { return "BaseText"; } } } class MyDerived : MyBase { public override string Text { get { string test = base.Text; return "DerivedText"; } } } Put a breakpoint on the last return statement, then run the code and access that property. In my VS2005, hovering over base.Text gives the value "DerivedText", but the variable test has been correctly set to "BaseText". So, new question: why does the debugger not handle base properly, and how can I get it to?

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  • Recipient address rejected: User unknown in local recipient table;

    - by Thufir
    I've gone through the guide for mailman with some difficulty, but seem to be nearly there. I'm able to navigate to the mailman web GUI, create lists and subscribe. I just subscribe my local FQDN, so [email protected] for testing purposes. This FQDN only works on localhost. However, e-mails to the list address, in this case [email protected], are rejected: root@dur:~# root@dur:~# tail /var/log/mail.log Aug 28 08:28:43 dur postfix/master[12208]: terminating on signal 15 Aug 28 08:28:44 dur postfix/postfix-script[12322]: starting the Postfix mail system Aug 28 08:28:44 dur postfix/master[12323]: daemon started -- version 2.9.1, configuration /etc/postfix Aug 28 08:28:46 dur postfix/postfix-script[12332]: stopping the Postfix mail system Aug 28 08:28:46 dur postfix/master[12323]: terminating on signal 15 Aug 28 08:28:47 dur postfix/postfix-script[12437]: starting the Postfix mail system Aug 28 08:28:47 dur postfix/master[12438]: daemon started -- version 2.9.1, configuration /etc/postfix Aug 28 08:29:29 dur postfix/smtpd[12460]: connect from localhost[127.0.0.1] Aug 28 08:29:30 dur postfix/smtpd[12460]: NOQUEUE: reject: RCPT from localhost[127.0.0.1]: 550 5.1.1 <[email protected]>: Recipient address rejected: User unknown in local recipient table; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<dur.bounceme.net> Aug 28 08:29:33 dur postfix/smtpd[12460]: disconnect from localhost[127.0.0.1] root@dur:~# root@dur:~# ll /var/lib/mailman/data/ total 56 drwxrwsr-x 2 root list 4096 Aug 28 08:28 ./ drwxrwsr-x 8 root list 4096 Aug 27 19:58 ../ -rw-r--r-- 1 root list 0 Aug 28 04:36 aliases -rw-r--r-- 1 root list 12288 Aug 28 04:36 aliases.db -rw-r--r-- 1 root list 12288 Aug 28 08:28 aliases.db.db -rw-r----- 1 root list 41 Aug 27 21:04 creator.pw -rw-rw-r-- 1 root list 10 Aug 27 19:58 last_mailman_version -rw-r--r-- 1 root list 14100 Oct 19 2011 sitelist.cfg root@dur:~# root@dur:~# grep alias /etc/postfix/main.cf alias_maps = hash:/etc/aliases, hash:/var/lib/mailman/data/aliases alias_database = hash:/var/lib/mailman/data/aliases.db #alias_database = hash:/etc/aliases root@dur:~# root@dur:~# postconf -n alias_database = hash:/var/lib/mailman/data/aliases.db alias_maps = hash:/etc/aliases, hash:/var/lib/mailman/data/aliases append_dot_mydomain = no biff = no broken_sasl_auth_clients = yes config_directory = /etc/postfix default_transport = smtp home_mailbox = Maildir/ inet_interfaces = loopback-only mailbox_command = /usr/lib/dovecot/deliver -c /etc/dovecot/conf.d/01-mail-stack-delivery.conf -m "${EXTENSION}" mailbox_size_limit = 0 mailman_destination_recipient_limit = 1 mydestination = $myhostname localhost.$mydomain localhost $mydomain myhostname = dur.bounceme.net mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 readme_directory = no recipient_delimiter = + relay_domains = lists.example.com relay_transport = relay relayhost = smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache smtp_use_tls = yes smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu) smtpd_recipient_restrictions = reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_pipelining, permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination smtpd_sasl_auth_enable = yes smtpd_sasl_authenticated_header = yes smtpd_sasl_local_domain = $myhostname smtpd_sasl_path = private/dovecot-auth smtpd_sasl_security_options = noanonymous smtpd_sasl_type = dovecot smtpd_tls_auth_only = yes smtpd_tls_cert_file = /etc/ssl/certs/ssl-mail.pem smtpd_tls_key_file = /etc/ssl/private/ssl-mail.key smtpd_tls_mandatory_ciphers = medium smtpd_tls_mandatory_protocols = SSLv3, TLSv1 smtpd_tls_received_header = yes smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache smtpd_use_tls = yes tls_random_source = dev:/dev/urandom transport_maps = hash:/etc/postfix/transport root@dur:~# Why is this e-mail rejected? It seems to, maybe be related to the alias_maps and alias_database settings in postfix.

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  • What's better in terms of user experience - providing an email address or a link to my projects github account?

    - by Oliver Weiler
    What's better in terms of user experience? Provide the user an email account where he can report bugs, or a link to the projects github issues page (which requires a github account but may be easier to submit bugs to)? EDIT The application is a Bash script hosted on github. The GNU Coding Standards suggests using an email address, which may or may not an appropriate solution. Target audience is the CLI power user.

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  • IPv6 - Public IPs, private IPs, IPs derived from the MAC address? Confused!

    - by sinni800
    I'm pretty much excited for IPv6 because of the large address room and (potential?) owning of more than one IP, or even tens of IPs (/122 subnet?) Though one magazine has now confused me. In a current issue (no. 3) of "CT", a German computer magazine, I read that when using IPv6 your IP address consists of your MAC address and various other things, and that this address will be public on the web, no matter what access point / LAN you connect to. My knowledge of IP(v6) is in contrary of this. I thought you will normally always have a a local network IP and NAT takes care of your Internet access, and your provider gives the NAT router an IP. I've heard of the 6to4 interface, but does this one give you your own ip in the IPv6 net? Personally I hope it still is through a personal IP space (like 192.168, 127.16-31, 10. in IPv4) in private networks with a NAT going to the Internet. And also I hope that providers will offer subnets to private customers so they don't have to use NAT anymore. Yay for converting your LAN into the WAN and using better security (so Computers from the same subnet still get access rights like normal).

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  • How to configure CISCO switch 2960 for port-based address allocation on a single port only?

    - by Jack
    CISCO 2960 allows you to configure so-called Port-Based address allocation. It makes the switch to associate IP address it is giving out via DHCP with port-identifier, which is random, switch created identifier. In practice it means that any machine connected to such configured port will always get the same IP address, regardless of what that machine's MAC address is. I want to have that feature configured on --some ports-- only. But no matter what commands I try it seems that this can only be done for all ports, all for none. Even though CISCO manual seems to indicate there's both global and per-port command to enable that. Here are relevant commands from CISCO manual: configure terminal ip dhcp use subscriber-id client-id (this configures the DHCP server to globally use the subscriber ID as the client ID on all incoming DHCP messages) interface FastEthernet0/1 ip dhcp server use subscriber-id client-id (Optional: Configures the DHCP server to use the subscriber ID as the client ID on all incoming DHCP messages on the interface) but it appears if I configure only per-interface than there's no effect at all, if I configure globally and per interface - CISCo behaves as if all ports were configured to use that feature. Any ideas?

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  • iptables: How to combine DNAT and SNAT to use a secondary IP address?

    - by Que_273
    There are lots of questions on here about iptables DNAT/SNAT setups but I haven't found one that solves my current problem. I have services bound to the IP address of eth0 (e.g. 192.168.0.20) and I also have a IP address on eth0:0 (192.168.0.40) which is shared with another server. Only one server is active, so this alias interface comes and goes depending on which server is active. In order to get traffic accepted by the service a DNAT rule is used to change the destination IP. iptables -t nat -A PREROUTING -d 192.168.0.40 -p udp --dport 7100 -j DNAT --to-destination 192.168.0.20 I also wish all outbound traffic from this service to appear to come from the shared IP, so that return responses will work in the event of a active-standby failover. iptables -t nat -A POSTROUTING -p udp --sport 7100 -j SNAT --to-source 192.168.0.40 My problem is that the SNAT rule is not always run. Inbound traffic causes a connection tracking entry like this. [root]# conntrack -L -p udp udp 17 170 src=192.168.0.185 dst=192.168.0.40 sport=7100 dport=7100 src=192.168.0.20 dst=192.168.0.185 sport=7100 dport=7100 [ASSURED] mark=0 secmark=0 use=2 which means the POSTROUTING chain is not run and outbound traffic leaves with the real IP address as the source. I am thinking I can set up a NOTRACK rule in the raw table to prevent conntracking for this port number, but is there a better or more efficient way to make this work? Edit - Alternative question: Is there a way (in CentOS/Linux) to have an interface that can be bound to but not used, such that it can be attached to the network or detached when a shared IP address is swapped between servers?

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  • C# 4.0: Covariance And Contravariance In Generics Made Easy

    - by Paulo Morgado
    In my last post, I went through what is variance in .NET 4.0 and C# 4.0 in a rather theoretical way. Now, I’m going to try to make it a bit more down to earth. Given: class Base { } class Derived : Base { } Such that: Trace.Assert(typeof(Base).IsClass && typeof(Derived).IsClass && typeof(Base).IsGreaterOrEqualTo(typeof(Derived))); Covariance interface ICovariantIn<out T> { } Trace.Assert(typeof(ICovariantIn<Base>).IsGreaterOrEqualTo(typeof(ICovariantIn<Derived>))); Contravariance interface ICovariantIn<out T> { } Trace.Assert(typeof(IContravariantIn<Derived>).IsGreaterOrEqualTo(typeof(IContravariantIn<Base>))); Invariance interface IInvariantIn<T> { } Trace.Assert(!typeof(IInvariantIn<Base>).IsGreaterOrEqualTo(typeof(IInvariantIn<Derived>)) && !typeof(IInvariantIn<Derived>).IsGreaterOrEqualTo(typeof(IInvariantIn<Base>))); Where: public static class TypeExtensions { public static bool IsGreaterOrEqualTo(this Type self, Type other) { return self.IsAssignableFrom(other); } }

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  • Recommened design pattern to handle multiple compression algorithms for a class hierarchy

    - by sgorozco
    For all you OOD experts. What would be the recommended way to model the following scenario? I have a certain class hierarchy similar to the following one: class Base { ... } class Derived1 : Base { ... } class Derived2 : Base { ... } ... Next, I would like to implement different compression/decompression engines for this hierarchy. (I already have code for several strategies that best handle different cases, like file compression, network stream compression, legacy system compression, etc.) I would like the compression strategy to be pluggable and chosen at runtime, however I'm not sure how to handle the class hierarchy. Currently I have a tighly-coupled design that looks like this: interface ICompressor { byte[] Compress(Base instance); } class Strategy1Compressor : ICompressor { byte[] Compress(Base instance) { // Common compression guts for Base class ... // if( instance is Derived1 ) { // Compression guts for Derived1 class } if( instance is Derived2 ) { // Compression guts for Derived2 class } // Additional compression logic to handle other class derivations ... } } As it is, whenever I add a new derived class inheriting from Base, I would have to modify all compression strategies to take into account this new class. Is there a design pattern that allows me to decouple this, and allow me to easily introduce more classes to the Base hierarchy and/or additional compression strategies?

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  • Interfaces on an abstract class

    - by insta
    My coworker and I have different opinions on the relationship between base classes and interfaces. I'm of the belief that a class should not implement an interface unless that class can be used when an implementation of the interface is required. In other words, I like to see code like this: interface IFooWorker { void Work(); } abstract class BaseWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker, IFooWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } The DbWorker is what gets the IFooWorker interface, because it is an instantiatable implementation of the interface. It completely fulfills the contract. My coworker prefers the nearly identical: interface IFooWorker { void Work(); } abstract class BaseWorker : IFooWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } Where the base class gets the interface, and by virtue of this all inheritors of the base class are of that interface as well. This bugs me but I can't come up with concrete reasons why, outside of "the base class cannot stand on its own as an implementation of the interface". What are the pros & cons of his method vs. mine, and why should one be used over another?

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  • How do I set a static DNS nameserver address on Ubuntu Server?

    - by Aleks
    I am trying statically to set DNS server addresses in my Ubuntu server running as virtual machine. I followed all recommendations on official Ubuntu support pages but I simply cannot get rid of my ISP's DNS servers set by DHCP. I assigned br0 interface on my host machine static IP address and eth0 on VM to use Google DNS and my own local DNS running on the second vm by setting it in /etc/network/interfaces. Tried to fiddle with head base and tail files in /etc/resolvconf/resolv.conf.d/ and tried to shuffle interface-order in /etc/resolvconf/interface-order but when I restarted network service I got the ISP's DNS addresses back every time. Is there a way that I can disable resolvconf and set up my resolv.conf file manually as I always did on Red Hat? Or at can you tell me which hook script keeps putting ISP DNSs in resolv.conf? My ISP don't allow me to change DHCP settings on my router so I cannot do it that way. Why is such a simple thing such as setting DNS servers got so complicated???

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  • Is this a good way to expose generic base class methods through an interface?

    - by Nate Heinrich
    I am trying to provide an interface to an abstract generic base class. I want to have a method exposed on the interface that consumes the generic type, but whose implementation is ultimately handled by the classes that inherit from my abstract generic base. However I don't want the subclasses to have to downcast to work with the generic type (as they already know what the type should be). Here is a simple version of the only way I can see to get it to work at the moment. public interface IFoo { void Process(Bar_base bar); } public abstract class FooBase<T> : IFoo where T : Bar_base { abstract void Process(T bar); // Explicit IFoo Implementation void IFoo.Process(Bar_base bar) { if (bar == null) throw new ArgumentNullException(); // Downcast here in base class (less for subclasses to worry about) T downcasted_bar = bar as T; if (downcasted_bar == null) { throw new InvalidOperationException( string.Format("Expected type '{0}', not type '{1}'", T.ToString(), bar.GetType().ToString()); } //Process downcasted object. Process(downcasted_bar); } } Then subclasses of FooBase would look like this... public class Foo_impl1 : FooBase<Bar_impl1> { void override Process(Bar_impl1 bar) { //No need to downcast here! } } Obviously this won't provide me compile time Type Checking, but I think it will get the job done... Questions: 1. Will this function as I think it will? 2. Is this the best way to do this? 3. What are the issues with doing it this way? 4. Can you suggest a different approach? Thanks!

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  • C++ Why is the converter constructor implicitly called?

    - by ShaChris23
    Why is the Child class's converter constructor called in the code below? I mean, it automatically converts Base to Child via the Child converter constructor. The code below compiles, but shouldn't it not compile since I haven't provided bool Child::operator!=(Base const&)? class Base { }; class Child : public Base { public: Child() {} Child(Base const& base_) : Base(base_) { std::cout <<"should never called!"; } bool operator!=(Child const&) { return true; } }; void main() { Base base; Child child; if(child != base) std::cout << "not equal"; else std::cout << "equal"; }

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