Commented Issue: Reflection exception when probing for WebAPI controllers [292]

I am trying to add webAPI to my existing .Net 4 RC app. When I try to access the webAPI route I get errors like:

<Exception xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/System.Web.Http.Dispatcher"><ExceptionType>System.IO.FileNotFoundException</ExceptionType><Message>Could not load file or assembly 'DevExpress.XtraEditors.v11.1, Version=11.1.8.0, Culture=neutral, PublicKeyToken=b88d1754d700e49a' or one of its dependencies. The system cannot find the file specified.</Message><StackTrace>
Server stack trace:
at System.Reflection.RuntimeAssembly.GetExportedTypes(RuntimeAssembly assembly, ObjectHandleOnStack retTypes)
at System.Reflection.RuntimeAssembly.GetExportedTypes()
at System.Web.Http.Dispatcher.DefaultHttpControllerTypeResolver.GetControllerTypes(IAssembliesResolver assembliesResolver)
at System.Web.Http.WebHost.WebHostHttpControllerTypeResolver.GetControllerTypes(IAssembliesResolver assembliesResolver)
at System.Web.Http.Dispatcher.HttpControllerTypeCache.InitializeCache()
at System.Lazy`1.CreateValue()

Exception rethrown at [0]:
at System.Reflection.RuntimeAssembly.GetExportedTypes(RuntimeAssembly assembly, ObjectHandleOnStack retTypes)
at System.Reflection.RuntimeAssembly.GetExportedTypes()
at System.Web.Http.Dispatcher.DefaultHttpControllerTypeResolver.GetControllerTypes(IAssembliesResolver assembliesResolver)
at System.Web.Http.WebHost.WebHostHttpControllerTypeResolver.GetControllerTypes(IAssembliesResolver assembliesResolver)
at System.Web.Http.Dispatcher.HttpControllerTypeCache.InitializeCache()
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at System.Lazy`1.get_Value()
at System.Web.Http.Dispatcher.DefaultHttpControllerSelector.InitializeControllerInfoCache()
at System.Lazy`1.CreateValue()

Exception rethrown at [1]:
at System.Reflection.RuntimeAssembly.GetExportedTypes(RuntimeAssembly assembly, ObjectHandleOnStack retTypes)
at System.Reflection.RuntimeAssembly.GetExportedTypes()
at System.Web.Http.Dispatcher.DefaultHttpControllerTypeResolver.GetControllerTypes(IAssembliesResolver assembliesResolver)
at System.Web.Http.WebHost.WebHostHttpControllerTypeResolver.GetControllerTypes(IAssembliesResolver assembliesResolver)
at System.Web.Http.Dispatcher.HttpControllerTypeCache.InitializeCache()
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at System.Lazy`1.get_Value()
at System.Web.Http.Dispatcher.DefaultHttpControllerSelector.InitializeControllerInfoCache()
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at System.Lazy`1.get_Value()
at System.Web.Http.Dispatcher.DefaultHttpControllerSelector.SelectController(HttpRequestMessage request)
at System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsyncInternal(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)</StackTrace></Exception>

BTW: Here is the code from MVC that is used by the area registration. It simply catches the error and moves on. I'm not sure why WebAPI doesn't do the same thing, or even use the same code.


private static IEnumerable<Type> FilterTypesInAssemblies(Predicate<Type> predicate) {
// Go through all assemblies referenced by the application and search for types matching a predicate
IEnumerable<Type> typesSoFar = Type.EmptyTypes;

ICollection assemblies = BuildManager.GetReferencedAssemblies();
foreach (Assembly assembly in assemblies) {
Type[] typesInAsm;
try {
typesInAsm = assembly.GetTypes();
}
catch (ReflectionTypeLoadException ex) {
typesInAsm = ex.Types;
}
typesSoFar = typesSoFar.Concat(typesInAsm);
}
return typesSoFar.Where(type => TypeIsPublicClass(type) && predicate(type));
}

Comments: This issue was fixed post-RC, much as the way you described. The fix will be available in the RTM version. Are you able to work around it until then? Probably the most common cause of the exception is having an assembly in the bin folder which depends on types in an assembly not in the bin folder. If type B derives from A, and type B's assembly is in bin but A's is not, you will see this kind of exception.