System.ArgumentException: Duplicate type name within an assembly - asp.net-mvc-3

Question

I am working on an ASP.Net MVC 3 web application using EF 4.1. Since today, I am getting this error:
System.ArgumentException: Duplicate type name within an assembly
and I can't figure out what is causing it. It is happening in my repository when performing a Find:
public virtual T GetById(long id)
{
return dbset.Find(id);
}
Here is the stack trace:
[ArgumentException: Duplicate type name within an assembly.]
System.Reflection.Emit.ModuleBuilder.CheckTypeNameConflict(String strTypeName, TypeBuilder enclosingType) +9544354
System.Reflection.Emit.AssemblyBuilderData.CheckTypeNameConflict(String strTypeName, TypeBuilder enclosingType) +53
System.Reflection.Emit.TypeBuilder.Init(String fullname, TypeAttributes attr, Type parent, Type[] interfaces, Module module, PackingSize iPackingSize, Int32 iTypeSize, TypeBuilder enclosingType) +178
System.Reflection.Emit.ModuleBuilder.DefineType(String name, TypeAttributes attr, Type parent, Type[] interfaces) +118
System.Data.Objects.Internal.ProxyTypeBuilder.get_TypeBuilder() +299
System.Data.Objects.Internal.ProxyTypeBuilder.CreateType(ModuleBuilder moduleBuilder) +227
System.Data.Objects.Internal.EntityProxyFactory.BuildType(ModuleBuilder moduleBuilder, ClrEntityType ospaceEntityType) +63
System.Data.Objects.Internal.EntityProxyFactory.TryCreateProxyType(EntityType ospaceEntityType) +193
System.Data.Objects.Internal.EntityProxyFactory.GetProxyType(ClrEntityType ospaceEntityType) +104
System.Data.Common.Internal.Materialization.Translator.Visit(EntityColumnMap columnMap, TranslatorArg arg) +178
System.Data.Query.InternalTrees.EntityColumnMap.Accept(ColumnMapVisitorWithResults`2 visitor, TArgType arg) +16
System.Data.Common.Internal.Materialization.Translator.ProcessCollectionColumnMap(CollectionColumnMap columnMap, TranslatorArg arg, ColumnMap discriminatorColumnMap, Object discriminatorValue) +116
System.Data.Common.Internal.Materialization.Translator.Visit(SimpleCollectionColumnMap columnMap, TranslatorArg arg) +13
System.Data.Query.InternalTrees.SimpleCollectionColumnMap.Accept(ColumnMapVisitorWithResults`2 visitor, TArgType arg) +17
System.Data.Common.Internal.Materialization.Translator.TranslateColumnMap(QueryCacheManager queryCacheManager, ColumnMap columnMap, MetadataWorkspace workspace, SpanIndex spanIndex, MergeOption mergeOption, Boolean valueLayer) +314
System.Data.Common.Internal.Materialization.TypedShaperFactoryCreator`1.TypedCreate(QueryCacheManager cacheManager, ColumnMap columnMap, MetadataWorkspace metadata, SpanIndex spanInfo, MergeOption mergeOption, Boolean valueLayer) +64
System.Data.Common.Internal.Materialization.ShaperFactory.Create(Type elementType, QueryCacheManager cacheManager, ColumnMap columnMap, MetadataWorkspace metadata, SpanIndex spanInfo, MergeOption mergeOption, Boolean valueLayer) +185
System.Data.Objects.Internal.ObjectQueryExecutionPlan.Prepare(ObjectContext context, DbQueryCommandTree tree, Type elementType, MergeOption mergeOption, Span span, ReadOnlyCollection`1 compiledQueryParameters) +285
System.Data.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption) +696
System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +149
System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() +44
System.Linq.Enumerable.SingleOrDefault(IEnumerable`1 source) +184
System.Data.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__2(IEnumerable`1 sequence) +41
System.Data.Objects.ELinq.ObjectQueryProvider.ExecuteSingle(IEnumerable`1 query, Expression queryRoot) +59
System.Data.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression) +150
System.Linq.Queryable.SingleOrDefault(IQueryable`1 source) +265
System.Data.Entity.Internal.Linq.InternalSet`1.FindInStore(WrappedEntityKey key, String keyValuesParamName) +602
System.Data.Entity.Internal.Linq.InternalSet`1.Find(Object[] keyValues) +124
System.Data.Entity.DbSet`1.Find(Object[] keyValues) +12
XXXXXXXX.Data.Infrastructure.RepositoryBase`1.GetById(Int64 id) in C:\XXXXXXXX\XXXXXXXX\XXXXXXXX.Data\Infrastructure\RepositoryBase.cs:58
MatchesHorsConcours.Service.MatchService.GetMatch(Int32 id) in C:\XXXXXXXX\XXXXXXXX\XXXXXXXX.Service\XxxService.cs:55
XXXXXXXX.Controllers.XXXXXXXX.Edit(Int32 id) in C:\XXXXXXXX\XXXXXXXX\XXXXXXXX.Web\Controllers\XxxController.cs:130
lambda_method(Closure , ControllerBase , Object[] ) +101
System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +17
System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +208
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +27
System.Web.Mvc.<>c__DisplayClass15.<InvokeActionMethodWithFilters>b__12() +55
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +263
System.Web.Mvc.<>c__DisplayClass17.<InvokeActionMethodWithFilters>b__14() +19
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +191
System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +343
System.Web.Mvc.Controller.ExecuteCore() +116
System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +97
System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10
System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +37
System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +21
System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +12
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
System.Web.Mvc.<>c__DisplayClasse.<EndProcessRequest>b__d() +50
System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +7
System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8920029
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184
This could be related to table in which I duplicated a foreign key. It was called something like myKeyId, and I now have myKey1Id and myKey2Id in that table. I checked everywhere in my code, and I can't find myKeyId anymore.
The error message is so generic that I don't know how to pin-point what is causing this error. Any advice would be welcome.

Answer 1

I hade the same error.
I did clean solution rebuilt and it worked.

Answer 2

My solution was to turn off IIS and then start VS project again.

Answer 3

I ran into this error today, too.
It turned out, that my data model has missing the foreign and primary key constraints in the data base.
I had copied the original database to a local database to speed up the execution, but I had only copied the data and not the relationships.
Other errors i had in this context were
an item with the same key has already been added
and
Unable to update the EntitySet Table because it has a DefiningQuery and no InsertFunction element exists in the ModificationFunctionMapping element to support the current operation
it all was due to a faultive database structure

Answer 4

Ran into this issue today. I deleted all of my tables from the Entity Model .edmx file, the updated my model from the Database (right-click --> update from database).
Then I re-compiled and it ran fine. Such an odd error.
I am running MVC 4 and EF 5.0