Reputation: 1905

The name does not exist in the namespace error in XAML

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?

Upvotes: 172

Answers (30)

BenKoshy

Reputation: 35725

It's worth a shot

In my case, the problem was a bug in Visual Studio.
The error didn't make any sense (in my case).
When i "rebuilt" - everything magically worked! After 45 minutes of frustration, this solution saved both my head and monitor from serious injury:

Solution: Try Re-building the solution

Short cut to re-build: CTRL + SHIFT + B

Solution 2: Try Restarting Visual Studio

Possibly VS have fixed the bug now: download the latest version if possible.

Upvotes: 0

Rick

Reputation: 841

What caused this problem for me was I had named a folder 'System' in my project.

I expect that this caused some kind of conflict/confusion with Microsoft's 'System' namespace.

Renaming 'System' to something else fixed it.

This will probably happen with other "reserved" Microsoft namespaces.

Upvotes: 0

DiskJunky

Reputation: 4991

Shoonya hit upon the same issue as I did, an overlap of namespaces in my local project with that of a referenced library. However, the solution is a little easier than "Create a new library and move your code".

Solution: ensure the namespace of any objects in your project don't overlap with that of an assembly. Moving the classes will work, but just editing your code/namespaces is sufficient.

Example to reproduce the issue;

Reference a library that you intend to use in XAML (like a control), e.g. SomeLibrary.Wpf
Have at least one object in your project with a namespace like MyProject.SomeLibrary

The XAML will no longer compile with a message saying "The name MyProject.SomeLibrary.Wpf does not exist"

It seems that the assembly resolver for the XAML references makes the assumption that if any object has a namespace that matches the start of a 3rd party reference, that all objects should be pulled from the local project.

Upvotes: 0

Beauty

Reputation: 965

In my case it was an upper case vs. lower case problem inside of the namespace. One single letter was different.

Compare exactly:

The namespace definition of your UserControl <UserControl x:Class="..."
The local definition of your UserControl xmlns:local="..."
The namespace definition of the parent UserControl xmlns:myNamespace="...", which you use to embed your UserControl.

The search function of Visual Studio is your friend, when you enable the option for case-sensitivity. If the namespace is different, it's not highlighted at all places.

If the case-sensitivity is your problem, then fix it, clean the solution, close Visual Studio, restart it and compile again.

Upvotes: 0

Younes Belouche

Reputation: 1520

For me, I created a custom control and a second Generic.xaml because I didn't notice that a new folder that contains the associated Generic.xaml was created. So I just removed the duplicated Generic.xaml that I created and modified the other one.

Upvotes: 0

nomacreates

Reputation: 147

Removing the sealed keyword from a class also takes away the error just in case one's classes are with that keyword. It worked for me!

Upvotes: 0

Kyle7286

Reputation: 13

FWIW... I was having this exact issue today and come to find out, it was due to opening my Solution/Project from a UNC Network Path instead of a mapped drive.

As soon as a mapped a drive to my repo and opened the project, it worked great.

TLDR: Try opening project from a mapped drive

Upvotes: 0

TheCoder

Reputation: 343

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.

Upvotes: 8

Octavian Niculescu

Reputation: 1327

I've stumbled accross the same problem too.

In my case, I deleted the x:class property from my XAML file by mistake and it didn't work anymore.

Upvotes: 0

JosephD

Reputation: 119

One more twist, in the hope that someone else may find it helpful. I had the same issue as everyone else here, and I tried all the suggestions--verified references, Debug/Release switch, restarted VS, checked build config level, rebuilt numerous times--and NOTHING HELPED. Finally, I tried the suggestion where I created a new Project and moved the one single object I was trying to resolve to that project, and THAT solved the reference issue.
However--and this is the reason I'm adding yet another post, here--eventually I figured out that the actual problem was that the original Project included one object referencing a SQLite database. It turned out that the installed NuGet SQLite package was actually causing the issue. When I moved the DB-accessing code and the NuGet SQLite reference to its own project, then I was able to move the original object back into the original project with all the others, and the referencing issue did not reappear. Evidently there's some setting in the NuGet SQLite package that was confusing the system.

Upvotes: 0

Abdullah Tahan

Reputation: 2129

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

Upvotes: 1

Ali Hus

Reputation: 255

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.

Upvotes: 1

Marius

Reputation: 1679

In Visual Studio 2019 I was able to fix it by changing the dropdown to Release as recommended in other answers. But when I changed back to Debug mode the error appeared again.

What fixed it for me in Debug mode:

Switch to Release mode
Click on "Disable project code" in the XAML Designer

Switch back to Debug mode => the error is gone

Upvotes: 0

le_fritz

Reputation: 51

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.

Upvotes: 4

Arsen Khachaturyan

Reputation: 8350

Try checking the References section, and see if there is a warning icon over the library reference you included:

If you see it then go to the Project -> Properties -> Application and make sure that both libraries are targeting the same version of the .NET framework.

P.S. When this issue happens it can also be noticed from the Warnings section:

Upvotes: 0

Yusuf Özcan

Reputation: 59

Add an empty constructor for your view model and rebuild solution.

Upvotes: -1

Skyfish

Reputation: 147

I had the same symptoms "The name does not exist in the namespace error", but the cause turned out to be different. I had a C: drive crash and had to reinstall Visual Studio 2017. I restored my source code files and opened the solution. Built it. No dice. As well as the "Name does not exist in the namespace" errors I noticed my sub-projects complaining that they couldn't find a MyProject.cs file ('MyProject' is not the actual project name, just used here as an example). I had a hunt for where MyProject.cs had gone, then remembered that there was never any such file! I looked in the Properties folders of each sub-project and found that Visual Studio had off its own back added bogus references to MyProject.cs!! I removed these references and now the solution builds fine like it used to.

Upvotes: -1

Casey

Reputation: 1

As another person posted this can be caused by saving the project on a network share. I found that if I switched from using a network path to a mapped network drive everything worked fine.

from: "\\SERVER\Programming\SolutionFolder"

to: "Z:\Programming\SolutionFolder" (exact mapping optional)

Upvotes: 0

SpaceballOne

Reputation: 11

A combination of two ideas in this thread worked for me, so I'll post what I did in the hopes that it helps someone else over the next 5 years that this problem continues. I'm using VS2017 Community)

Delete reference to dll
Clean, Rebuild, Build
Close VS, Unblock the dll (see note below), Delete shadow cache
Open VS, Clean, Rebuild, Build
Restore reference to dll
Clean, Rebuild, Build

I may not have the order exactly right in steps 2, 4, and 6 but I was grasping at straws after spending nearly 2 hours with this problem. I think the key for me was the combination of removing the reference, unblocking the dll and deleting the shadow cache.

(Note for step 3 - The dll I'm using was written by a coworker/mentor of mine, so I know it's safe. Careful with this step if you don't know the source of your dll)

I'll be bookmarking this thread for posterity, since it appears that MS has no desire to clean this stuff up. WPF is hard enough to learn on it's own, and having to hack through stuff like this when you've done everything right is infuriating. 🤬🤬🤬

Upvotes: 0

Cauly

Reputation: 540

In my case, this problem will happen when the wpf program's architechture is not exactly same with dependency. Suppose you have one dependency that is x64, and another one is AnyCPU. Then if you choose x64, the type in AnyCPU dll will "does not exist", otherwise the type in x64 dll will "does not exist". You just cannot emilate both of them.

Upvotes: 0

eric gilbertson

Reputation: 1003

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

Upvotes: 2

user1040323

Reputation: 501

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.

Upvotes: 1

PI Mike

Reputation: 1

I had the added the assembly as a project - first deleted the ddl that was added specifically to the references to the dll - that did it.

Upvotes: 0

kad81

Reputation: 10950

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).

Upvotes: 1

Sean

Reputation: 2667

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

Upvotes: 1

1iveowl

Reputation: 1732

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.

Upvotes: 35

Corne

Reputation: 1

Also try to right click on your project->properties and change Platform target to Any CPU and rebuild, it will then work. This worked for me

Upvotes: 0

Jonas

Reputation: 1214

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.

Upvotes: 10

teynon

Reputation: 8318

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.

Upvotes: 24

Shoonya

Reputation: 128

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.

Upvotes: 4

The name does not exist in the namespace error in XAML

Answers (30)

It's worth a shot

Solution: Try Re-building the solution

Solution 2: Try Restarting Visual Studio

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