That's cool (that's real not sarcastic), it's good to know the real reason for why it happens (and that it's not something we did wrong). I still think maybe the implementation leaves a bit to be desired, but hey it's a first release and maybe there was no way around it anyway. I still would place it pretty high my wish list (along with visual inheritance for webforms).
Thanks again, John Deal -----Original Message----- From: Marsh, Drew [mailto:[EMAIL PROTECTED]] Sent: Wednesday, May 22, 2002 12:08 PM To: [EMAIL PROTECTED] Subject: Re: [DOTNET] ASP.Net Abstract Base Page Inheritance DEAL John M [mailto:[EMAIL PROTECTED]] wrote: > I don't quite buy into the "designer attempts to instantiate the Page > class... and of course it can't instantiate an > *abstract* class" aspect of it. The point is the page that is being > designed is a concrete version of the abstract class and it is that > concrete class that should be being instantiated (no different than at > runtime). I could buy if it complained that I hadn't implemented an > abstract method in my concrete class, but not that the designer should > be trying to instantiate the abstract itself (what would be the point > of inheritance if you never got to the concrete class?). I'm > really not trying to be difficult, I just don't see why the > designer would ever try and instantiate the abstract class. Ok... lemme break this down for ya a bit. Here's what I've come to understand while diving into the guts of this stuff for fun. When designing a WebForm, it instantiates the base Page class, *not* the Page class being designed. So when this happens in your scenario you get: System.Runtime.Serialization.SerializationException: Type Abstract at Microsoft.VSDesigner.WebForms.RootCodeDomSerializer.Deserialize(IDesignerSer ializationManager manager, Object codeObject) at Microsoft.VisualStudio.Designer.Serialization.CodeDomLoader.Load() at Microsoft.VisualStudio.Designer.Serialization.BaseDesignerLoader.Load() Specifically, this comes from the following IL: <codeSnippet language="C#"> IL_0160: callvirt instance string [System]System.CodeDom.CodeTypeReference::get_BaseType() IL_0165: stelem.ref IL_0166: ldloc.s V_8 IL_0168: call string Microsoft.VSDesigner.SR::GetString(string, object[]) IL_016d: newobj instance void [mscorlib]System.Runtime.Serialization.SerializationException::.ctor(string) IL_0172: throw IL_0173: ldloc.s V_7 IL_0175: callvirt instance bool [mscorlib]System.Type::get_IsAbstract() IL_017a: brfalse.s IL_01a1 IL_017c: ldstr "WFD_TypeAbstract" IL_0181: ldc.i4.1 IL_0182: newarr [mscorlib]System.Object IL_0187: stloc.s V_8 IL_0189: ldloc.s V_8 IL_018b: ldc.i4.0 IL_018c: ldloc.s V_7 IL_018e: callvirt instance string [mscorlib]System.Type::get_FullName() IL_0193: stelem.ref IL_0194: ldloc.s V_8 IL_0196: call string Microsoft.VSDesigner.SR::GetString(string, object[]) IL_019b: newobj instance void [mscorlib]System.Runtime.Serialization.SerializationException::.ctor(string) IL_01a0: throw </codeSnippet> Basically, IL_0160 get's the base type of the page class in preparation to instantiate it for help with design. However, you see at IL_0175 the check to make sure it's not abstract. Since your base class is abstract, you get the error you're seeing. Otherwise IL_017a breaks to IL_01a1 which eventually leads to instantiating the base class and continues forward with design. HTH, Drew .NET MVP You can read messages from the DOTNET archive, unsubscribe from DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com. You can read messages from the DOTNET archive, unsubscribe from DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.
