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• How to change the Struts2 validation error message in the case of an invalid field value?

  - by FarmBoy

  I'm using Struts2 validation on a web form. In the case that a field is suppose to be an integer or Date, the <s:fielderror> message I receive is a generic Invalid field value for field "[fieldname]" Naturally, I want to customize this for the user. Here's an example validation: <field name="spouseDOB"> <field-validator type="date"> <message>"Spouse Date of Birth" is invalid.</message> </field-validator> <field-validator type="date"> <param name="min">01/01/1900</param> <message>"Spouse Date of Birth" must be after 1900 AD. </field-validator> </field> The message "Spouse Date of Birth" is invalid. never appears, for any invalid date that I have tried. The output is the generic Invalid field value for field spouseDOB spouseDOB is a java.util.Date object in the action class. It is set by a <s:textfield> in the JSP.

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• Spatial Rotation in Gmod Expression2.

  - by Fascia

  I'm using expression2 to program behavior in Garry's mod (http://wiki.garrysmod.com/?title=Wire_Expression2) Okay so, to set the precedent. In Gmod I have a block and I am at a complete loss of how to get it to rotate around the 3 up, down and right vectors (Which are local. ie; if I pitch it 45 degrees the forward vector is 0.707, 0.707, 0). Essentially, From the 3 vectors I'd like to be able to get local Pitch/Roll/Yaw. By Local Pitch Roll Yaw I mean that they are completely independent of one another allowing true 3d rotation. So for example; if I place my craft so its nose is parallel to the floor the X,Y,Z would be 0,0,0. If I turn it parallel to the floor (World and Local Yaw) 90 degrees it's now 0, 0, 90. If I then pitch it (World Roll, Local Pitch) it 180 degrees it's now 180, 0, 90. I've already explored quaternions however I don't believe I should post my code here as I think I was re-inventing the wheel. I know I didn't explain that well but I believe the problem is pretty generic. Any help anyone could offer is greatly appreciated. Oh, I'd like to avoid gimblelock too. Essentially calculating the rotation around each of the crafts up/forward/right vectors using the up/forward/right vectors. To simply the question a generic implementation rather than one specific to Gmod is absolutely fine.

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• DataContract Known Types - passing array

  - by Erup

  Im having problems when passing an generic List, trough a WCF operation. In this case, there is a List of int. The example 4 is described here in MSDN. Note that in MSDN sample, is described: // This will serialize and deserialize successfully because the generic List is equivalent to int[], which was added to known types. Above, is the DataContract: [DataContract] [KnownType(typeof(int[]))] [KnownType(typeof(object[]))] public class AccountData { [DataMember] public object accNumber1; [DataMember] public object accNumber2; [DataMember] public object accNumber3; [DataMember] public object accNumber4; } In client side, Im calling the operation like this: DataTransfer.Service.AccountData data = new DataTransfer.Service.AccountData() { accNumber1 = 100, accNumber2 = new int[100], accNumber3 = new List<int>(), accNumber4 = new ArrayList() }; cService.AddAccounts(data); Also, here is the decorations of the generated AccountData obj (WCF proxy): [System.Diagnostics.DebuggerStepThroughAttribute()] [System.CodeDom.Compiler.GeneratedCodeAttribute("System.Runtime.Serialization", "3.0.0.0")] [System.Runtime.Serialization.DataContractAttribute(Name="AccountData", Namespace="http://schemas.datacontract.org/2004/07/DataTransfer.Service")] [System.SerializableAttribute()] [System.Runtime.Serialization.KnownTypeAttribute(typeof(DataTransfer.Client.CustomerServiceReference.PurchaseOrder))] [System.Runtime.Serialization.KnownTypeAttribute(typeof(DataTransfer.Client.CustomerServiceReference.Customer))] [System.Runtime.Serialization.KnownTypeAttribute(typeof(int[]))] [System.Runtime.Serialization.KnownTypeAttribute(typeof(object[]))]

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• Why is ExecuteFunction method only available through base.ExecuteFunction in a child class of Object

  - by Matt

  I'm trying to call ObjectContext.ExecuteFunction from my objectcontext object in the repository of my site. The repository is generic, so all I have is an ObjectContext object, rather than one that actually represents my specific one from the Entity Framework. Here's an example of code that was generated that uses the ExecuteFunction method: [global::System.CodeDom.Compiler.GeneratedCode("System.Data.Entity.Design.EntityClassGenerator", "4.0.0.0")] public global::System.Data.Objects.ObjectResult<ArtistSearchVariation> FindSearchVariation(string source) { global::System.Data.Objects.ObjectParameter sourceParameter; if ((source != null)) { sourceParameter = new global::System.Data.Objects.ObjectParameter("Source", source); } else { sourceParameter = new global::System.Data.Objects.ObjectParameter("Source", typeof(string)); } return base.ExecuteFunction<ArtistSearchVariation>("FindSearchVariation", sourceParameter); } But what I would like to do is something like this... public class Repository<E, C> : IRepository<E, C>, IDisposable where E : EntityObject where C : ObjectContext { private readonly C _ctx; // ... public ObjectResult<E> ExecuteFunction(string functionName, params[]) { // Create object parameters return _ctx.ExecuteFunction<E>(functionName, /* parameters */) } } Anyone know why I have to call ExecuteFunction from base instead of _ctx? Also, is there any way to do something like I've written out? I would really like to keep my repository generic, but with having to execute stored procedures it's looking more and more difficult... Thanks, Matt

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• Why isn't my WPF Datagrid showing data?

  - by Edward Tanguay

  This walkthrough says you can create a WPF datagrid in one line but doesn't give a full example. So I created an example using a generic list and connected it to the WPF datagrid, but it doesn't show any data. What do I need to change on the code below to get it to show data in the datagrid? ANSWER: This code works now: XAML: <Window x:Class="TestDatagrid345.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:toolkit="http://schemas.microsoft.com/wpf/2008/toolkit" xmlns:local="clr-namespace:TestDatagrid345" Title="Window1" Height="300" Width="300" Loaded="Window_Loaded"> <StackPanel> <toolkit:DataGrid ItemsSource="{Binding}"/> </StackPanel> </Window> Code Behind: using System.Collections.Generic; using System.Windows; namespace TestDatagrid345 { public partial class Window1 : Window { private List<Customer> _customers = new List<Customer>(); public List<Customer> Customers { get { return _customers; }} public Window1() { InitializeComponent(); } private void Window_Loaded(object sender, RoutedEventArgs e) { DataContext = Customers; Customers.Add(new Customer { FirstName = "Tom", LastName = "Jones" }); Customers.Add(new Customer { FirstName = "Joe", LastName = "Thompson" }); Customers.Add(new Customer { FirstName = "Jill", LastName = "Smith" }); } } }

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• Binary Search Tree in Java

  - by John R

  I want to make a generic BST, that can be made up of any data type, but i'm not sure how I could add things to the tree, if my BST is generic. All of my needed code is below. I want my BST made up of Locations, and sorted by the x variable. Any help is appreciated. Major thanks for looking. public void add(E element) { if (root == null) root = element; if (element < root) add(element, root.leftChild); if (element > root) add(element, root.rightChild); else System.out.println("Element Already Exists"); } private void add(E element, E currLoc) { if (currLoc == null) currLoc = element; if (element < root) add(element, currLoc.leftChild); if (element > root) add(element, currLoc.rightChild); else System.out.println("Element Already Exists); } Other Code public class BinaryNode<E> { E BinaryNode; BinaryNode nextBinaryNode; BinaryNode prevBinaryNode; public BinaryNode() { BinaryNode = null; nextBinaryNode = null; prevBinaryNode = null; } } public class Location<AnyType> extends BinaryNode { String name; int x,y; public Location() { name = null; x = 0; y = 0; } public Location(String newName, int xCord, int yCord) { name = newName; x = xCord; y = yCord; } public int equals(Location otherScene) { return name.compareToIgnoreCase(otherScene.name); } }

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• Inherited fluent nhibenate mapping issue

  - by Aim Kai

  I have an interesting issue today!! Basically I have two classes. public class A : B { public virtual new ISet<DifferentItem> Items {get;set;} } public class B { public virtual int Id {get;set;} public virtual ISet<Item> Items {get;set;} } The subclass A hides the base class B property, Items and replaces it with a new property with the same name and a different type. The mappings for these classes are public class AMapping : SubclassMap<A> { public AMapping() { HasMany(x=>x.Items) .LazyLoad() .AsSet(); } } public class BMapping : ClassMap<B> { public BMapping() { Id(x=>x.Id); HasMany(x=>x.Items) .LazyLoad() .AsSet(); } } However when I run my unit test to check the mapping I get the following exception: Tests the A mapping: NHibernate.PropertyAccessException : Invalid Cast (check your mapping for property type mismatches); setter of A ---- System.InvalidCastException : Unable to cast object of type 'NHibernate.Collection.Generic.PersistentGenericSet1[Item]' to type 'Iesi.Collections.Generic.ISet1[DifferentItem]'. Anyone have any ideas? Clearly it is something to do with the type of the collection on the sub-class. But I skimmed through the available options on the mapping class and nothing stood out as being the solution here.

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• How do I best handle a needed patch for Perl/Tk?

  - by Streamline

  I am making a change to Perl/Tk for an application that has its own resident Perl and modules installation (so we can drop the app in and go). I've found a problem I am experiencing that I just stumbled on what seems to be the patch I need here: http://osdir.com/ml/lang.perl.tk/2004-10/msg00030.html Bug confirmed. Here's the patch against Tk804.027: --- Tk-804.027/pTk/mTk/generic/tkEntry.c Sat Mar 20 19:54:48 2004 +++ Tk-804.027-perl5.8.3d/pTk/mTk/generic/tkEntry.c Tue Oct 19 22:50:31 2004 @@ -3478,6 +3478,18 @@ Tcl_DStringFree(&script); #else + switch (type) { + case VALIDATE_INSERT: + type = 1; + break; + case VALIDATE_DELETE: + type = 0; + break; + default: + type = -1; + break; + } + code = LangDoCallback(entryPtr-interp, entryPtr-validateCmd, 1, 5, "%s %s %s %d %d", new, change, entryPtr-string, index, type); if (code != TCL_OK && code != TCL_RETURN) { Regards, Slaven I'd like to apply this patch or if there is a newer version of the Perl/Tk module I can upgrade to that includes this patch already that doesn't require I change the version of Perl, do that. Here is what I can find from the installation for this app: perl -v = 5.8.4 $Tk::version = '8.4' $Tk::patchlevel = '8.4' $Tk::VERSION = '804.027' So.. 1a) if there is a newer Tk VERSION that includes the patch in the link above, how do I upgrade just that module in the specific Perl installation location for this app? 1b) how do I know if that upgrade is compatible with 5.8.4 of Perl (I don't want to upgrade perl at this point) 2) if not, how do I apply that patch defined in that link?

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• Databinding problem in dropdownlist box by generics in C#

  - by sakir-ali

  I want to implement stack in my program by Genericx. I have a textbox and button to add elements in stack, a dropdownlist box and a button to bind total stack in dropdownlist box. I have generic class and the code is below: [Serializable] public class myGenClass<T> { private T[] _elements; private int _pointer; public myGenClass(int size) { _elements = new T[size]; _pointer = 0; } public void Push(T item) { if (_pointer > _elements.Length - 1) { throw new Exception("Stack is full"); } _elements[_pointer] = item; _pointer++; } public T Pop() { _pointer--; if (_pointer < 0) { throw new Exception("Stack is empty"); } return _elements[_pointer]; } public T[] myBind() { T[] showall = new T[_pointer]; Array.Copy(_elements,showall, _pointer); T[] newarray = showall; Array.Reverse(showall); return showall; } } and my .cs page is below: public partial class _Default : System.Web.UI.Page { myGenClass<int> mystack = new myGenClass<int>(25); protected void Button1_Click(object sender, EventArgs e) { mystack.Push(Int32.Parse(TextBox1.Text)); //DropDownList1.Items.Add(mystack.Pop().ToString()); TextBox1.Text = string.Empty; TextBox1.Focus(); } protected void Button2_Click(object sender, EventArgs e) { //string[] db; //db = Array.ConvertAll<int, string>(mystack.myBind(), Convert.ToString); DropDownList1.DataSource = mystack.myBind(); DropDownList1.DataBind(); } } but when I bind the datasource property of dropdownlist box to generic type return array (i.e. myBind()), it shows empty... Please help..

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• Removing padding from structure in kernel module

  - by dexkid

  I am compiling a kernel module, containing a structure of size 34, using the standard command. make -C /lib/modules/$(KVERSION)/build M=$(PWD) modules The sizeof(some_structure) is coming as 36 instead of 34 i.e. the compiler is padding the structure. How do I remove this padding? Running make V=1 shows the gcc compiler options passed as make -I../inc -C /lib/modules/2.6.29.4-167.fc11.i686.PAE/build M=/home/vishal/20100426_eth_vishal/organised_eth/src modules make[1]: Entering directory `/usr/src/kernels/2.6.29.4-167.fc11.i686.PAE' test -e include/linux/autoconf.h -a -e include/config/auto.conf || ( \ echo; \ echo " ERROR: Kernel configuration is invalid."; \ echo " include/linux/autoconf.h or include/config/auto.conf are missing."; \ echo " Run 'make oldconfig && make prepare' on kernel src to fix it."; \ echo; \ /bin/false) mkdir -p /home/vishal/20100426_eth_vishal/organised_eth/src/.tmp_versions ; rm -f /home/vishal/20100426_eth_vishal/organised_eth/src/.tmp_versions/* make -f scripts/Makefile.build obj=/home/vishal/20100426_eth_vishal/organised_eth/src gcc -Wp,-MD,/home/vishal/20100426_eth_vishal/organised_eth/src/.eth_main.o.d -nostdinc -isystem /usr/lib/gcc/i586-redhat-linux/4.4.0/include -Iinclude -I/usr/src/kernels/2.6.29.4-167.fc11.i686.PAE/arch/x86/include -include include/linux/autoconf.h -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Os -m32 -msoft-float -mregparm=3 -freg-struct-return -mpreferred-stack-boundary=2 -march=i686 -mtune=generic -Wa,-mtune=generic32 -ffreestanding -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1 -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -Iarch/x86/include/asm/mach-generic -Iarch/x86/include/asm/mach-default -Wframe-larger-than=1024 -fno-stack-protector -fno-omit-frame-pointer -fno-optimize-sibling-calls -g -pg -Wdeclaration-after-statement -Wno-pointer-sign -fwrapv -fno-dwarf2-cfi-asm -DTX_DESCRIPTOR_IN_SYSTEM_MEMORY -DRX_DESCRIPTOR_IN_SYSTEM_MEMORY -DTX_BUFFER_IN_SYSTEM_MEMORY -DRX_BUFFER_IN_SYSTEM_MEMORY -DALTERNATE_DESCRIPTORS -DEXT_8_BYTE_DESCRIPTOR -O0 -Wall -DT_ETH_1588_051 -DALTERNATE_DESCRIPTORS -DEXT_8_BYTE_DESCRIPTOR -DNETHERNET_INTERRUPTS -DETH_IEEE1588_TESTS -DSNAPTYPSEL_TMSTRENA_TEVENTENA_TESTS -DT_ETH_1588_140_147 -DLOW_DEBUG_PRINTS -DMEDIUM_DEBUG_PRINTS -DHIGH_DEBUG_PRINTS -DMODULE -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(eth_main)" -D"KBUILD_MODNAME=KBUILD_STR(conxt_eth)" -c -o /home/vishal/20100426_eth_vishal/organised_eth/src/eth_main.o /home/vishal/20100426_eth_vishal/organised_eth/src/eth_main.c

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• Typecasting EnityObject

  - by AJ

  Hello, I'm new to C# and am stuck on the following. I have a Silverlight web service that uses LINQ to query a ADO.NET entity object. e.g.: [OperationContract] public List<Customer> GetData() { using (TestEntities ctx = new TestEntities()) { var data = from rec in ctx.Customer select rec; return data.ToList(); } } This works fine, but what I want to do is to make this more abstract. The first step would be to return a List<EntityObject> but this gives a compiler error, e.g.: [OperationContract] public List<EntityObject> GetData() { using (TestEntities ctx = new TestEntities()) { var data = from rec in ctx.Customer select rec; return data.ToList(); } } The error is: Error 1 Cannot implicitly convert type 'System.Collections.Generic.List<SilverlightTest.Web.Customer>' to 'System.Collections.Generic.IEnumerable<System.Data.Objects.DataClasses.EntityObject>'. An explicit conversion exists (are you missing a cast?) What am i doing wrong? Thanks, AJ

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• Mono ASP.NET Oracle Connection

  - by bladepit

  Hello to everybody, if i want to connect to orcale i became the following error: libclntsh.so Description: HTTP 500. Error processing request. Stack Trace: System.DllNotFoundException: libclntsh.so at (wrapper managed-to-native) System.Data.OracleClient.Oci.OciCalls/OciNativeCalls.OCIEnvCreate (intptr&,System.Data.OracleClient.Oci.OciEnvironmentMode,intptr,intptr,intptr,intptr,int,intptr) <0x0005d at System.Data.OracleClient.Oci.OciCalls.OCIEnvCreate (intptr&,System.Data.OracleClient.Oci.OciEnvironmentMode,intptr,intptr,intptr,intptr,int,intptr) [0x00000] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient.Oci/OciCalls.cs:738 at System.Data.OracleClient.Oci.OciEnvironmentHandle..ctor (System.Data.OracleClient.Oci.OciEnvironmentMode) [0x00013] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient.Oci/OciEnvironmentHandle.cs:35 at System.Data.OracleClient.Oci.OciGlue.CreateConnection (System.Data.OracleClient.OracleConnectionInfo) [0x00000] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OciGlue.cs:86 at System.Data.OracleClient.OracleConnectionPoolManager.CreateConnection (System.Data.OracleClient.OracleConnectionInfo) [0x00006] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnectionPoolManager.cs:57 at System.Data.OracleClient.OracleConnectionPool.CreateConnection () [0x0000e] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnectionPool.cs:97 at System.Data.OracleClient.OracleConnectionPool.GetConnection () [0x000ba] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnectionPool.cs:74 at System.Data.OracleClient.OracleConnection.Open () [0x00061] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnection.cs:410 at WebServer.Controllers.HomeController.Index () [0x00006] in /home/bhcweb/Projects/Controllers/HomeController.cs:19 at (wrapper dynamic-method) System.Runtime.CompilerServices.ExecutionScope.lambda_method (System.Runtime.CompilerServices.ExecutionScope,System.Web.Mvc.ControllerBase,object[]) <0x00080 at System.Web.Mvc.ActionMethodDispatcher.Execute (System.Web.Mvc.ControllerBase,object[]) <0x0001b at System.Web.Mvc.ReflectedActionDescriptor.Execute (System.Web.Mvc.ControllerContext,System.Collections.Generic.IDictionary2<string, object>) <0x000fd> at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod (System.Web.Mvc.ControllerContext,System.Web.Mvc.ActionDescriptor,System.Collections.Generic.IDictionary2) <0x0001c at System.Web.Mvc.ControllerActionInvoker/c_AnonStoreyB.<m_E () <0x00067 at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter (System.Web.Mvc.IActionFilter,System.Web.Mvc.ActionExecutingContext,System.Func`1) <0x000c4 What is my Problem there? I have read that i have to set my ORACLE_HOME AND LD_LIBRARY_PATH. If i do echo $ORACLE_HOME and $LD_LIBRARY_PATH the path which i have set is coming out: /usr/lib/oracle/xe/app/oracle/product/10.2.0/client/lib This is the path where the libclntsh.so is in. Is this right? Best regards bladepit

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• Newbie question about controllers in ASP.Net MVC.

  - by Sergio Tapia

  I'm following a tutorial on creating the NerdDinner using ASP.Net MVC. However, I'm using Visual Studio 2010 Ultimate edition and there was only MVC2 to choose from. So I've following the tutorial so far, and everything is really clicking and being really well explained, until this little hitch. The guide is asking me to create new methods on a Controller file like so: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; namespace NerdDinner.Controllers { public class DinnersController : Controller { public void Index(){ Response.Write("<h1>Coming Soon: Dinners</h1>"); } public void Details(int id) { Response.Write("<h1>Details DinnerID: " + id + "</h1>"); } } } However, when I created the Controllers file, Visual Studio created an Index method already, but it looks vastly different to what the tutorial shows. Maybe this is the new way to do things using MVC2? using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; namespace NerdDinner.Controllers { public class DinnersController : Controller { // // GET: /Dinners/ public ActionResult Index() { return View(); } } } My question is, how can I reproduce the Details and Index method (they're in MVC) to the MVC2 way? Is this even relevant? Thank you!

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• Maintain denormalized data with NHibernate EventListener

  - by Michael Valenty

  I have one bit of denormalized data used for performance reasons and I'm trying to maintain the data with an NHibernate event listener rather than a trigger. I'm not convinced this is the best approach, but I'm neck deep into it and I want to figure this out before moving on. I'm getting following error: System.InvalidOperationException : Collection was modified; enumeration operation may not execute. System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) System.Collections.Generic.List`1.Enumerator.MoveNextRare() System.Collections.Generic.List`1.Enumerator.MoveNext() NHibernate.Engine.ActionQueue.ExecuteActions(IList list) NHibernate.Engine.ActionQueue.ExecuteActions() NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions (IEventSource session) NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event) NHibernate.Impl.SessionImpl.Flush() NHibernate.Transaction.AdoTransaction.Commit() Here's the code to make happen: using (var tx = session.BeginTransaction()) { var business = session .Get<Business>(1234) .ChangeZipCodeTo("92011"); session.Update(business); tx.Commit(); // error happens here } and the event listener: public void OnPostUpdate(PostUpdateEvent @event) { var business = @event.Entity as Business; if (business != null) { var links = @event.Session .CreateQuery("select l from BusinessCategoryLink as l where l.Business.BusinessId = :businessId") .SetParameter("businessId", business.BusinessId) .List<BusinessCategoryLink>(); foreach (var link in links) { link.Location = business.Location; @event.Session.Update(link); } } }

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• Covariance and Contravariance type inference in C# 4.0

  - by devoured elysium

  When we define our interfaces in C# 4.0, we are allowed to mark each of the generic parameters as in or out. If we try to set a generic parameter as out and that'd lead to a problem, the compiler raises an error, not allowing us to do that. Question: If the compiler has ways of inferring what are valid uses for both covariance (out) and contravariance(in), why do we have to mark interfaces as such? Wouldn't it be enough to just let us define the interfaces as we always did, and when we tried to use them in our client code, raise an error if we tried to use them in an un-safe way? Example: interface MyInterface<out T> { T abracadabra(); } //works OK interface MyInterface2<in T> { T abracadabra(); } //compiler raises an error. //This makes me think that the compiler is cappable //of understanding what situations might generate //run-time problems and then prohibits them. Also, isn't it what Java does in the same situation? From what I recall, you just do something like IMyInterface<? extends whatever> myInterface; //covariance IMyInterface<? super whatever> myInterface2; //contravariance Or am I mixing things? Thanks

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• Debugging mono assembly load error

  - by Will I Am

  I am running asp.net/mono on Ubuntu with lighthttpd/fastcgi. Somehow I suspect an assembly reference sneaked in that I cannot track down, and it's causing my application to fail (it works fine on windows under MS.NET). When I try it under mono, I get: Failed to create shadow copy (CopyFile). Description: HTTP 500. Error processing request. Stack Trace: System.ExecutionEngineException: Failed to create shadow copy (CopyFile). at (wrapper managed-to-native) System.Reflection.Assembly:LoadFrom (string,bool) at System.Reflection.Assembly.LoadFrom (System.String assemblyFile) [0x00000] at System.Web.Compilation.BuildManager.LoadAssembly (System.String path, System.Collections.Generic.List`1 al) [0x00000] at System.Web.Compilation.BuildManager.GetReferencedAssemblies () [0x00000] at System.Web.Compilation.BuildManager.GenerateAssembly (System.Web.Compilation.AssemblyBuilder abuilder, System.Collections.Generic.List`1 buildItems, System.Web.VirtualPath virtualPath, BuildKind buildKind) [0x00000] at System.Web.Compilation.BuildManager.BuildAssembly (System.Web.VirtualPath virtualPath) [0x00000] at System.Web.Compilation.BuildManager.GetCompiledType (System.String virtualPath) [0x00000] at System.Web.HttpApplicationFactory.InitType (System.Web.HttpContext context) [0x00000] Version information: Mono Version: 2.0.50727.1433; ASP.NET Version: 2.0.50727.1433 I am at a loss to how to debug this, as it's not giving me a hint of what assembly it's having problem with. Any ideas?

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• Q on Python serialization/deserialization

  - by neil

  What chances do I have to instantiate, keep and serialize/deserialize to/from binary data Python classes reflecting this pattern (adopted from RFC 2246 [TLS]): enum { apple, orange } VariantTag; struct { uint16 number; opaque string<0..10>; /* variable length */ } V1; struct { uint32 number; opaque string[10]; /* fixed length */ } V2; struct { select (VariantTag) { /* value of selector is implicit */ case apple: V1; /* VariantBody, tag = apple */ case orange: V2; /* VariantBody, tag = orange */ } variant_body; /* optional label on variant */ } VariantRecord; Basically I would have to define a (variant) class VariantRecord, which varies depending on the value of VariantTag. That's not that difficult. The challenge is to find a most generic way to build a class, which serializes/deserializes to and from a byte stream... Pickle, Google protocol buffer, marshal is all not an option. I made little success with having an explicit "def serialize" in my class, but I'm not very happy with it, because it's not generic enough. I hope I could express the problem. My current solution in case VariantTag = apple would look like this, but I don't like it too much import binascii import struct class VariantRecord(object): def __init__(self, number, opaque): self.number = number self.opaque = opaque def serialize(self): out = struct.pack('>HB%ds' % len(self.opaque), self.number, len(self.opaque), self.opaque) return out v = VariantRecord(10, 'Hello') print binascii.hexlify(v.serialize()) >> 000a0548656c6c6f Regards

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• Factory Pattern: Determining concrete factory class instantiation?

  - by Chris

  I'm trying to learn patterns and I'm stuck on determining how or where a Factory Pattern determines what class to instanciate. If I have a Application that calls the factory and sends it, say, an xml config file to determine what type of action to take, where does that logic for interpreting the config file happen? THE FACTORY using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace myNamespace { public abstract class SourceFactory { abstract public UploadSource getUploadSource(); } public class TextSourceFactory : SourceFactory { public override UploadSource getUploadSource() { return new TextUploadSource(); } } public class XmlSourceFacotry : SourceFactory { public override UploadSource getUploadSource() { return new XmlUploadSource(); } } public class SqlSourceFactory : SourceFactory { public override UploadSource getUploadSource() { return new SqlUploadSource(); } } } THE CLASSES using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace myNamespace { public abstract class UploadSource { abstract public void Execute(); } public class TextUploadSource : UploadSource { public override void Execute() { Console.WriteLine("You executed a text upload source"); } } public class XmlUploadSource : UploadSource { public override void Execute() { Console.WriteLine("You executed an XML upload source"); } } public class SqlUploadSource : UploadSource { public override void Execute() { Console.WriteLine("You executed a SQL upload source"); } } }

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• Why is Collection<String>.class Illegal?

  - by Peter

  I am puzzled by generics. You can declare a field like: Class<Collection<String>> clazz = ... It seems logical that you could assign this field with: Class<Collection<String>> clazz = Collection<String>.class; However, this generates an error: Syntax error on token ">", void expected after this token So it looks like the .class operator does not work with generics. So I tried: class A<S> {} class B extends A<String> {} Class<A<String>> c = B.class; Also does not work, generates: Type mismatch: cannot convert from Class<Test.StringCollection> to Class<Collection<String>> Now, I really fail to see why this should not work. I know generic types are not reified but in both cases it seems to be fully type safe without having access to runtime generic types. Anybody an idea? Peter Kriens

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• Covariance and Contravariance inference in C# 4.0

  - by devoured elysium

  When we define our interfaces in C# 4.0, we are allowed to mark each of the generic parameters as in or out. If we try to set a generic parameter as out and that'd lead to a problem, the compiler raises an error, not allowing us to do that. Question: If the compiler has ways of inferring what are valid uses for both covariance (out) and contravariance(in), why do we have to mark interfaces as such? Wouldn't it be enough to just let us define the interfaces as we always did, and when we tried to use them in our client code, raise an error if we tried to use them in an un-safe way? Example: interface MyInterface<out T> { T abracadabra(); } //works OK interface MyInterface2<in T> { T abracadabra(); } //compiler raises an error. //This makes me think that the compiler is cappable //of understanding what situations might generate //run-time problems and then prohibits them. Also, isn't it what Java does in the same situation? From what I recall, you just do something like IMyInterface<? extends whatever> myInterface; //covariance IMyInterface<? super whatever> myInterface2; //contravariance Or am I mixing things? Thanks

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• C# style Action<T>, Func<T,T>, etc in C++0x

  - by Austin Hyde

  C# has generic function types such as Action<T> or Func<T,U,V,...> With the advent of C++0x and the ability to have template typedef's and variadic template parameters, it seems this should be possible. The obvious solution to me would be this: template <typename T> using Action<T> = void (*)(T); however, this does not accommodate for functors or C++0x lambdas, and beyond that, does not compile with the error "expected unqualified-id before 'using'" My next attempt was to perhaps use boost::function: template <typename T> using Action<T> = boost::function<void (T)>; This doesn't compile either, for the same reason. My only other idea would be STL style template arguments: template <typename T, typename Action> void foo(T value, Action f) { f(value); } But this doesn't provide a strongly typed solution, and is only relevant inside the templated function. Now, I will be the first to admit that I am not the C++ wiz I prefer to think I am, so it's very possible there is an obvious solution I'm not seeing. Is it possible to have C# style generic function types in C++?

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• Sort and limit queryset by comment count and date using queryset.extra() (django)

  - by thornomad

  I am trying to sort/narrow a queryset of objects based on the number of comments each object has as well as by the timeframe during which the comments were posted. Am using a queryset.extra() method (using django_comments which utilizes generic foreign keys). I got the idea for using queryset.extra() (and the code) from here. This is a follow-up question to my initial question yesterday (which shows I am making some progress). Current Code: What I have so far works in that it will sort by the number of comments; however, I want to extend the functionality and also be able to pass a time frame argument (eg, 7 days) and return an ordered list of the most commented posts in that time frame. Here is what my view looks like with the basic functionality in tact: import datetime from django.contrib.comments.models import Comment from django.contrib.contenttypes.models import ContentType from django.db.models import Count, Sum from django.views.generic.list_detail import object_list def custom_object_list(request, queryset, *args, **kwargs): '''Extending the list_detail.object_list to allow some sorting. Example: http://example.com/video?sort_by=comments&days=7 Would get a list of the videos sorted by most comments in the last seven days. ''' try: # this is where I started working on the date business ... days = int(request.GET.get('days', None)) period = datetime.datetime.utcnow() - datetime.timedelta(days=int(days)) except (ValueError, TypeError): days = None period = None sort_by = request.GET.get('sort_by', None) ctype = ContentType.objects.get_for_model(queryset.model) if sort_by == 'comments': queryset = queryset.extra(select={ 'count' : """ SELECT COUNT(*) AS comment_count FROM django_comments WHERE content_type_id=%s AND object_pk=%s.%s """ % ( ctype.pk, queryset.model._meta.db_table, queryset.model._meta.pk.name ), }, order_by=['-count']).order_by('-count', '-created') return object_list(request, queryset, *args, **kwargs) What I've Tried: I am not well versed in SQL but I did try just to add another WHERE criteria by hand to see if I could make some progress: SELECT COUNT(*) AS comment_count FROM django_comments WHERE content_type_id=%s AND object_pk=%s.%s AND submit_date='2010-05-01 12:00:00' But that didn't do anything except mess around with my sort order. Any ideas on how I can add this extra layer of functionality? Thanks for any help or insight.

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• Generics vs inheritance (whenh no collection classes are involved)

  - by Ram

  This is an extension of this questionand probably might even be a duplicate of some other question(If so, please forgive me). I see from MSDN that generics are usually used with collections The most common use for generic classes is with collections like linked lists, hash tables, stacks, queues, trees and so on where operations such as adding and removing items from the collection are performed in much the same way regardless of the type of data being stored. The examples I have seen also validate the above statement. Can someone give a valid use of generics in a real-life scenario which does not involve any collections ? Pedantically, I was thinking about making an example which does not involve collections public class Animal<T> { public void Speak() { Console.WriteLine("I am an Animal and my type is " + typeof(T).ToString()); } public void Eat() { //Eat food } } public class Dog { public void WhoAmI() { Console.WriteLine(this.GetType().ToString()); } } and "An Animal of type Dog" will be Animal<Dog> magic = new Animal<Dog>(); It is entirely possible to have Dog getting inherited from Animal (Assuming a non-generic version of Animal)Dog:Animal Therefore Dog is an Animal Another example I was thinking was a BankAccount. It can be BankAccount<Checking>,BankAccount<Savings>. This can very well be Checking:BankAccount and Savings:BankAccount. Are there any best practices to determine if we should go with generics or with inheritance ?

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• Compilation Error: "The modifier 'public' is not valid for this item" while creating public method o

  - by Lalit

  I am getting this error while creating public method on a class for explicitly implementing the interface. I have the workaround: by removing the explicit implementation of PrintName Method, But surprised why i am getting this error. Can anyone explain the error. Code for Library: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Test.Lib1 { public class Customer : i1 { public string i1.PrintName() //Error Here... { return this.GetType().Name + " called from interface i1"; } } public interface i1 { string PrintName(); } interface i2 { string PrintName(); } } Code for Console Test Application: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Test.Lib1; namespace ca1.Test { class Program { static void Main(string[] args) { Customer customer = new Customer(); Console.WriteLine(customer.PrintName()); //i1 i1o = new Customer(); //Console.WriteLine(i1o.printname()); //i2 i2o = new Customer(); //Console.WriteLine(i2o.printname()); } } }

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• Did the Unity Team fix that "generics handling" bug back in 2008?

  - by rasx

  At my level of experience with Unity it might be faster to ask whether the "generics handling" bug acknowledged by ctavares back in 2008 was fixed in a public release. Here was the problem (which might be my problem today): Hi, I get an exception when using .... container.RegisterType(typeof(IDictionary<,), typeof(Dictionary<,)); The exception is... "Resolution of the dependency failed, type = \"IDictionary2\", name = \"\". Exception message is: The current build operation (build key Build Key[System.Collections.Generic.Dictionary2[System.String,System.String], null]) failed: The current build operation (build key Build Key[System.Collections.Generic.Dictionary2[System.String,System.String], null]) failed: The type Dictionary2 has multiple constructors of length 2. Unable to disambiguate. When I attempt... IDictionary myExampleDictionary = container.Resolve(); Here was the moderated response: There are no books that'll help, Unity is a little too new for publishers to have caught up yet. Unfortunately, you've run into a bug in our generics handling. This is currently fixed in our internal version, but it'll be a little while before we can get the bits out. In the meantime, as a workaround you could do something like this instead: public class WorkaroundDictionary : Dictionary { public WorkaroundDictionary() { } } container.RegisterType(typeof(IDictionary<,),typeof(WorkaroundDictionary<,)); The WorkaroundDictionary only has the default constructor so it'll inject no problem. Since the rest of your app is written in terms of IDictionary, when we get the fixed version done you can just replace the registration with the real Dictionary class, throw out the workaround, and everything will still just work. Sorry about the bug, it'll be fixed soon!

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