The name does not exist in the namespace error in

Question

Using VS2012 working on a VB.NET WPF application. I have a simple MusicPlayer tutorial app I am using to learn WPF. I am converting a C# version of the tutorial to VB.NET step by step.

It has 2 classes in the app that are both under the same namespace. I am able to reference the namespace in the XAML but when I try to reference the class object in XAML I get an error and I am not able to compile.

Strange thing is that the IntelliSense works fine with both referencing the namespace via the xmlns:c= tag and also when typing the class object using <c: But the object is underlined and errors are generated trying to build or work in the designer.

The .vb class files are in a folder called \Controls. The Main project Root Namespace is intentionaly left blank. The class is coded like this...

Namespace MusicPlayer.Controls
    Public Class UpdatingMediaElement
       .... code here
    End Public
End Namespace

The xaml looks like this

(namespace defined in the <Window > tag

xmlns:c="clr-namespace:MusicPlayer.Controls"

(object defined in a <Grid> )

  <c:UpdatingMediaElement Name="MyMediaElement" />

(error displayed) The name "UpdatingMediaElement" does not exist in the namespace "clr-namespace:MusicPlayer.Controls".

Not sure what is wrong or how to fix it?

Answer 1

If the assembly is different from the namespace in which your class is contained, you have to specfiy it explicitly.

ex:-

xmlns:Local="clr-namespace:MusicPlayer.Controls;assembly=MusicPlayer"

Answer 2

I went through all the answers and none helped me. Finally was able to solve it by myself, so presenting the answer as it might help others.

In my case, the solution had two projects, one containing the models (say the project and assembly name was Models) and another containing the views and view models (as per our convention: project, assembly name and default namespace were Models.Monitor). The Models.Monitor referred Models project.

In the Models.Monitor project, in one of the xaml I included the following namespace: xmlns:monitor="clr-namespace:Models.Monitor"

I suspect that MsBuild and Visual Studio then were erroring out as they were trying to find a 'Monitor' type in the assembly 'Models'. To resolve I tried the following:

1. xmlns:monitor="clr-namespace:Models.Monitor;assembly=" - which is valid if the namespace is in same assembly as per https://msdn.microsoft.com/en-us/library/ms747086(v=vs.110).aspx
2. also tried the explicit namespace declaration: xmlns:monitor="clr-namespace:Models.Monitor;assembly=Models.Monitor"

Neither of the above worked.

Finally I gave up, and as a work around moved the UserControl I was trying to use to another namespace: 'ModelsMonitor'. I was able to compile fine after that.

Answer 3

VB.NET does not automatically add the Namespace information based on the folder structure as it does in C#. I think I am going through the same tutorial as you (Teach Yourself WPF in 24 Hours), and doing the same conversion to VB.

I found you have to manually add the Namespace information to Both the XAML Class and the XAML.VB code behind to be able to use the Namespaces as described in the book. Even then, VB doesn't automatically Assign the Namespace to the Assembly as it does in VB.

There is another article here that shows how to include this in your project templates so it does build the Namespace information automatically - Automatically add namespace when adding new item

Answer 4

In my case it was because of other compile errors. When other errors have been solved this seemingly related error was also removed from the list. Specially the errors at the bottom of the errors list and on pages you have recently changed.

So do not pay attention to this error directly and focus on other errors at first.

Answer 5

Looks like this problem may be solved through a variety of "tricks."

In my case, I had been building/rebuilding/cleaning the entire solution, instead of just the project that I was working on within the solution. Once I clicked "Build [my project]," the error message went away.

Answer 6

When you are writing your wpf code and VS tell that "The name ABCDE does not exist in the namespace clr-namespace:ABC". But you can totally build your project successfully, there is only a small inconvenience because you can not see the UI designing (or just want to clean the code).

Try to do these:

• In VS, right click on your Solution -> Properties -> Configuration Properties

• A new dialog is opened, try to change the project configurations from Debug to Release or vice versa.

After that, re-build your solution. It can solve your problem.