Xaml Designer crashes

Question

I'm using VS 2012 in my project, and i've got such XAML designer crush.

Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteException

No connection string named '************' could be found in the application config file.
   at System.Data.Entity.Internal.LazyInternalConnection.get_ConnectionHasModel()
   at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
   at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)
   at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()
   at System.Data.Entity.Internal.Linq.InternalSet`1.GetEnumerator()
   at System.Data.Entity.Infrastructure.DbQuery`1.System.Collections.Generic.IEnumerable<TResult>.GetEnumerator()
   at *************.ViewModel.**********.<GetReferralList>b__1d() in d:\******.cs:line 422
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at ***************.<GetReferralList>d__29.MoveNext() in *******************\MainTabViewModel.cs:line 391
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__1(Object state)
   at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()

And here is the code that creates the issue

await Task.Run(() =>
        {
            using (var context = new SCMEntities())
            {
                var listOfGenRefReg = context.GenericReferralRegistrationIs;
                foreach (var item in listOfGenRefReg)
                {
                         Application.Current.Dispatcher.Invoke(() =>
                            LastReferrals.Add(item));

                }

            }

Answer 1

It is ideal to have a ViewModel for the designer and another for runtime. This depends on how you are wiring your MainTabViewModel to your View . Use the following snippet in your View to determine when it is executing in a designer:

bool isInDesignMode = DesignerProperties.GetIsInDesignMode(this)

where this is your View .

You should use the result to skip any database-related execution.

Answer 2

You are trying to access a database which does not work in the designer. You need to refactor your code so that you can use design time data if necessary and the database only at runtime.