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.NET Forum / .NET Framework / New Users / July 2007Strange Compile Problem With Generics
I've tried to debug this every way I can think of, but I can't figure out this strange compile problem I am having. Any help is greatly appreciated. I have a generic collection class that inherits from System.Collections.ObjectModel.Collection(Of T) called MatrixGenericCollectionBase (Matrix is the name of our project). Despite it's name it is actually an instantiable class that is used widely in our application to hold objects of many types. There is some additional functionality in the class but for the most part it is just a normal implementation of a generic collection, not a ton of additional code. In one instance I need a type specific collection because I need to add a function at the collection level that is specific for that type. In this case I have created a new class that inherits from MatrixGenericCollectionBase(Of TypeX) and named the new collection class TypeXCollection. The only code this class contains is the new function, which basically just loops through the collection and looks for specific members based on some parameters passed in. This compiles and runs fine when I compile through Visual Studio on my local machine. It also compiles fine when I run my nAnt build scripts on my local machine. It compiles fine when compiled in the VS IDE on the build server. BUT, it fails when the nAnt build script is run on the build server. The compile error I receive is "error BC30311: Value of type 'T' cannot be converted to 'Matrix.TypeX'". This error is received on a line of code that is iterating through the collection in a for each statement. I have mapped a drive to the code on the build server and run the nAnt scripts locally against the build server code and it compiles fine. I have copied the command line call to vbc that is shown in the output window of Visual Studio when I compile in release mode and run it from a command line and it fails with the same error. That's right, the same thing that is succeeding for Visual Studio on the same box is failing for me. I've now even gone as far as uninstalling and reinstalling the .Net 2.0 framework. I'm frustrated and ready to go back to the old non-generic base collection just to be able to compile on my build server. If you have any ideas, please help. Just to share some extra weirdness... I tried running msbuild on the build server against the project file expecting to get a clean compile the same as I do through VS 2005. Wrong! It gave me the same error I described below. Why in the world would the MSBuild results be different than the results I get through the IDE? Doesn't the IDE just call MSBuild? Can someone at least confirm for me that I am not crazy and that the code situation I described *should* compile? > Just to share some extra weirdness... > [quoted text clipped - 3 lines] > MSBuild results be different than the results I get through the IDE? Doesn't > the IDE just call MSBuild? I don't have any specific knowledge regarding that question, but given the behavior I'd say perhaps it doesn't. Alternatively, maybe there are some compiler switches that are different. That's the first thing I'd look at. > Can someone at least confirm for me that I am not crazy and that the code > situation I described *should* compile? I'm not sure anyone can do that until you actually post a complete-but-concise sample of code that reliably reproduces the problem. Pete Comments below: > > Just to share some extra weirdness... > > [quoted text clipped - 9 lines] > Alternatively, maybe there are some compiler switches that are > different. That's the first thing I'd look at. It was the first thing I looked at too, that is why I copied the vbc call and all parameters from the output window of VS 2005 and pasted it into a command prompt window. Either VS 2005 isn't showing me all of the parameters it is setting or something else is causing the difference. Either way if someone can tell me how to figure out how to run the vb compiler exactly the same way VS 2005 is I'd be mighty grateful. > > Can someone at least confirm for me that I am not crazy and that the code > > situation I described *should* compile? > > I'm not sure anyone can do that until you actually post a > complete-but-concise sample of code that reliably reproduces the problem. I'm afraid to spend too much time paring the code down to a useable sample because I'm not sure if anyone will be able to reproduce the problem. Right now I can only recreate the problem on one box, it just happens to be our build server. But maybe if I can reproduce it on the build server someone else will be able to reproduce it too; I'll see what I can put together quickly. 'Matrix.TypeX' inherits from ? It could be quite easy to forget that your collection inherits from its parent but it doesn't mean that the type you are using to store your elements inherits from the type you used for elements when inheriting from your base collection - hopefully you'll better understand than me what I'm trying to say ;-) --- Patrice > Just to share some extra weirdness... > [quoted text clipped - 7 lines] > Can someone at least confirm for me that I am not crazy and that the code > situation I described *should* compile? Thanks for the suggestion Patrice but the generic type parameters for the collection I'm inheriting from and the type of the members I am putting into the collection match. I even tried swithching it to declare the type specific collection as a generic collection with a constraint for the specific type I want to hold and then passing the type parameter through to the class I'm inheriting from and I still got the same compile error in the same situations. > 'Matrix.TypeX' inherits from ? > [quoted text clipped - 18 lines] > > Can someone at least confirm for me that I am not crazy and that the code > > situation I described *should* compile? Well I'm no closer to knowing what causes it to compile sometimes and sometimes not, but I've narrowed down what it is choking on. It appears to be specifically related to the enumerator. If I change the code that is throwing an error to use a for loop with an index instead of a for each loop it works fine. > I've tried to debug this every way I can think of, but I can't figure out > this strange compile problem I am having. Any help is greatly appreciated. [quoted text clipped - 34 lines] > just to be able to compile on my build server. If you have any ideas, please > help. The MatrixGenericCollectionBase object was inheriting System.Collections.ObjectModel.Collection(Of T) and was also implementing IDictionary since it is sort of hybrid dictionary/collection [dumb I know, cleaning up code one step at a time]. Apparently since both of those implement IEnumerable it seems like there was some sort of clash. I still can't explain why it worked in some environments and not in others but at least I know how to start to fix it. > Well I'm no closer to knowing what causes it to compile sometimes and > sometimes not, but I've narrowed down what it is choking on. It appears to [quoted text clipped - 40 lines] > > just to be able to compile on my build server. If you have any ideas, please > > help.
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