The name does not exist in the namespace error in XAML - wpf

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

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.

Answer 2

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 3

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 4

I've seen this issue go away by clearing the Xaml Design Shadow Cache. I had the issue with Visual Studio 2015 Update 1.
In Visual Studio 2015 the Cache is located here:
%localappdata%\Microsoft\VisualStudio\14.0\Designer\ShadowCache
Process:
Right-Click on the solution in the Solution Explorer and Choose "Clean Solution"
Shutdown Visual Studio
Delete the ShadowCache folder
Reopened the Visual Studio project
Rebuild the solution
And voila no more namespace errors.

Answer 5

Try changing the build target platform to x86 and building the project.
I noticed via Subversion that I apparently changed the project build Platform target to x64. This was the only change I had made. After making that change, the code was working for a short while before it started showing the same error you experienced. I changed the platform target to x86 to test and suddenly my designer was working again. Subsequently, I changed it back to x64, and the problem has disappeared completely. I suspect that the designer builds some kind of cached code in x32 and changing the x64 build platform breaks it when you make code changes.

Answer 6

Maybe another solution for when the project compiles but the XAML error is showing :
In solution explore, on the project node that contains the xaml
Right-click on the project and choose 'Unload Project'
Right-click on the project and choose 'Reload Project'
Make sure that your project is still choosen as "startup project". If not :
Right-click on the project and choose 'Set as startup project'
No need to rebuild, or close visual studio.

Answer 7

Jesus... This is still a problem five years later in Visual Studio 2017. Since I'm new to WPF, I was sure the problem was somehow me, but no, everything compiled and ran correctly.
I tried rebuilding, cleaning and rebuilding, switching between x86/x64 output, rebooting Windows, cleaning the ShadowCache folder, adding ";assembly={my main assembly name}" to the XML namespace declaration, nothing worked! The single thing that did:
Put my static class of Commands (in my case the deal was about making the design discover my WPF Commands) in its separate assembly and changing the assembly name to that one's instead.

Answer 8

Dunno if this will help anyone else
I'm new to WPF and still a novice with VB.net - so I was assuming that getting this error was being caused by me doing summit silly........ suppose I was really! I've managed to get rid of it by moving my project from a shared drive to one of my local drives.
Error's disappeared, project compiles perfectly no further issues - yet. Looks like VS2015 still has problems with projects held on a shared drive.

Answer 9

I had this problem recently using VS 2015 Update 3 for my WPF project in .NET 4.6.2. The copy of my project was in a network folder, I moved it locally and that solved the problem.
This may solve other sort of problems, as it looks like VS 2015 doesn't like network paths. Another issue that is a big problem for them is syncing git repositories if my project is in a network path, also solved by moving it locally.

Answer 10

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:
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
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 11

I'm also having a lot of trouble with this one! Intellisense helps me complete the namespace and everything, but the compiler cries. I've tried everything I found in this and other threads. However in my case what helped in the end was writing something like this:
xmlns:util="clr-namespace:LiveSpielTool.Utils;assembly="
Leaving the assembly name empty. No idea why. But it was mentioned here. I must add I am developing an assembly, so the assembly attribute might make sense. But entering the assembly name did not work. So weird.

Answer 12

I had the same problem , and in my case the the Markup Design View asked me to rebuild the solution and did not show me the form layout with this message:
Design view is unavailable for x64 and ARM target platforms, or Build the Project to update Design view.
It does not get solved by rebuilding the solution (neither the design view nor the "The name does not exist in the namespace" error)
I think it was because I had played with the settings on Solution -> Properties > Configuration Properties
I finally resolved the problem with 2 jobs:
Checking all check boxes on Build Column of the page: Solution -> Properties -> Configuration Properties
Changing the solution configurations from Debug to Release or vice versa.
I think it's a bug in Visual Studio2012 Update 2.

Answer 13

The same problem plagues Visual Studios 2013, Service Pack 4.
I also tried it with Visual Studios 2015 Preview with the same results.
It's just a limitation of the WPF visualizer which the Visual Studios team hasn't fixed.
As proof, building in x86 mode enables the visualizer and building in x64 mode disables it.
Strangely enough intellisense works for Visual Studios 2013, Service Pack 4.

Answer 14

In my case the problem was due to some phantom files under the project's obj directory. The following fixed the issue for me:
Clean project
Exit VS
rm -rf /obj/*
Invoke VS and rebuild

Answer 15

In my case, it was just a weird bug.
I had the class I was trying to use in my namespace however Visual Studio kept throwing an error saying the class did not exist in the given namespace.
What I did to fix it was really silly but worked like a charm.
I commented out all the lines of code where I was trying to use the class, cleaned the build, rebuilt and the project was up and running.
Then I just uncommented the lines of code I had commented earlier and well, Visual Studio was no longer throwing me any errors.
Rebuild again and you are ready to go.

Answer 16

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 17

Try verifying your assembly references. If you have a yellow exclamation mark on the project references there's a problem there and you'll get all kinds of errors.
If you know the project reference is correct, check the Target framework. For instance, having a project using the 4.5 framework reference a project with 4.5.2 framework is not a good combination.

Answer 18

The solution for me was to unblock the assembly DLLs. The error messages you get don't indicate this, but the XAML designer refuses to load what it calls "sandboxed" assemblies. You can see this in the output window when you build. DLLs are blocked if they are downloaded from the internet. To unblock your 3rd-party assembly DLLs:
Right click on the DLL file in Windows Explorer and select Properties.
At the bottom of the General tab click the "Unblock" button or checkbox.
Note: Only unblock DLLs if you are sure they are safe.

Answer 19

In my case, the user control was added to the main project. I tried various solutions above to no avail. Either I would get Invalid Markup but the solution would compile and work, or I would add the
xmlns:c="clr-namespace:MyProject;assembly=MyProject" and then the markup would show, but I would get a compile error that the tag does not exist in the XML namespace.
Finally, I added a new WPF User Control Library project to the solution and moved my user control from the main project into that one. Added the reference and changed the assembly to point to the new library and finally the markup worked and the project compiled without error.

Answer 20

In my case I had a namespace and class spelled exactly the same, so for example, one of my namespaces was
firstDepth.secondDepth.Fubar
which contains its own classes (e.g. firstDepth.secondDepth.Fubar.someclass)
but I also had a 'Fubar' class in the namespace
firstDepth.secondDepth
which textually resolves to the same as the Fubar namespace above.
Don't do this

Answer 21

This problem can also be caused if the assembly that you're referencing isn't actually built. For example, if your xaml is in Assembly1 and you're referencing a class also in Assembly1, but that assembly has errors and isn't building, this error will be shown.
I feel silly about it, but in my case I was tearing asunder a user control and had all sorts of errors in the related classes as a result. As I was attempting to fix them all I started with the errors in question, not realising that xaml relies on built assemblies to find these references (unlike c#/vb code which can work it out even before you build).

Answer 22

I get this problem all the time. My views are in a WPF Custom Control Library project (a variant on Class Library). I can reference pre-built assemblies, but cannot reference any code in another project of the same solution. As soon as I move the code to the same project as the xaml it's recognized.

Answer 23

This happened to me already twice in a complex WPF app, in it there are 4 multi platform projects, 1 shared project, 2 support libraries, and 1 test project..
This very specific XAML namespace error happened twice on very recently modified files on the Shared project. In both of my cases, it was a new c# file added with a repeating namespace entry;
Like namespace MyProgram.MyFolder.MyProgram.MyFolder
I double pasted it once by mistake, and once it was due to JetBrains Rider double pasting the namespace. (If you ever rename a project in Rider, it time to time starts double pasting namespaces on new file creations, especially on Shared projects..). These c# files with repeating namespaces were then called in the ViewModels where XAML files were referencing to. Well you then get these unrelated and misleading errors, you can have a problem with one file, all your Xaml files will start erroring out eventually.
Anyways, if you get these kind of errors, it's most of the time an issue on a very newly added file or code change. My suggestions would be to look at your very recent changes.

Answer 24

If non of the answers worked
For me was .Net Framework version compatibility issue of the one i'm using was older then what is referencing
From properties => Application then target framework

Answer 25

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 26

In the solution property page, check the platform of the assembly that contains "UpdatingMediaElement" and the assmeblies that contain any of the superclasses and interfaces from which "UpdatingMediaElement" subclasses or implements. It appears that the platform of all these assemblies must be "AnyCPU".

Answer 27

Another possible cause: A post-build event is removing the project DLL from the build folder.
To clarify: WPF designer may report "The name XXX does not exist in the namespace...", even when the name does exist in the namespace and the project builds and runs just fine if a post-build event removes the project DLL from the build folder (bin\Debug, bin\Release, etc.). I have personal experience with this in Visual Studio 2015.

Answer 28

Ok, so none of these tips worked for me, unfortunately. I was able to eventually solve the issue. It seems that Visual Studio does not play nicely with network drives. I solved this issue by moving the project from the shared drive to my local and recompiled. No more errors.

Answer 29

Adding to the pile.
Mine was the assembly name of the WPF application was the same assembly name as a referenced dll. So make sure you don't have duplicate assembly names in any of your projects.

Answer 30

I had the solution stored on a network share and every time I opened it I would get the warning about untrusted sources. I moved it to a local drive and the "namespace does not exist" error went away as well.