Metadata file '.dll' could not be found – Dev

The best answers to the question “Metadata file '.dll' could not be found” in the category Dev.


I am working on a WPF, C# 3.0 project, and I get this error:

Error 1 Metadata file
'WORK=- \Tools\VersionManagementSystem\BusinessLogicLayer\bin\Debug
\BusinessLogicLayer.dll' could not be found C:\-=WORK=- \Tools
\VersionManagementSystem\VersionManagementSystem\CSC VersionManagementSystem

This is how I reference my usercontrols:

<vms:SignOffProjectListing Margin="5"/>

It happens after every failed build. The only way I can get the solution to compile is to comment out all my user controls and re-build the project, and then I uncomment the usercontrols and everything is fine.

I have checked build orders and dependencies configurations.

As you can see, it seems to have truncated the DLL file’s absolute path… I have read that there is a bug with the length. Is this a possible problem?

It’s very annoying and having to comment, build, and uncomment, the build is becoming extremely tiresome.


This can still happen in newer versions of Visual Studio (I just had it happen on Visual Studio 2013):

Another thing to try is to close Visual Studio and delete the .suo file that is next to the .sln file. (It will be re-generated the next time you Save all (or exit Visual Studio)).

I’ve had this problem when adding new projects to the solution on another machine and then pulling the revisions in, but the .suo file can be corrupted in other cases as well and lead to very strange Visual Studio behaviour, so deleting it is one of the things I always try.

Note that deleting the .suo file will reset the startup project(s) of the solution.

More on the .suo file is here.


I just had the same problem. Visual Studio isn’t building the project that’s being referenced.

Written Instructions:

  1. Right click on the solution and click Properties.
  2. Click Configuration on the left.
  3. Make sure the check box under “Build” for the project it can’t find is checked. If it is already checked, uncheck, hit apply and check the boxes again.
  4. (Optional) You had to do it for both Release and Debug modes on the solution properties.

Screen capture Instructions:

  • They say a picture is worth a thousand words. Click on the GIF to zoom in, and hopefully it will be easy to follow:

Gif Instructions


Well, my answer is not just the summary of all the solutions, but it offers more than that.

Section (1):

In general solutions:

I had four errors of this kind (‘metadata file could not be found’) along with one error saying ‘Source File Could Not Be Opened (‘Unspecified error ‘)’.

I tried to get rid of ‘metadata file could not be found’ error. For that, I read many posts, blogs, etc. and found these solutions may be effective (summarizing them over here):

  1. Restart Visual Studio and try building again.

  2. Go to ‘Solution Explorer’. Right click on Solution. Go to Properties. Go to ‘Configuration Manager’. Check if the checkboxes under ‘Build’ are checked or not. If any or all of them are unchecked, then check them and try building again.

  3. If the above solution(s) do not work, then follow sequence mentioned in step 2 above, and even if all the checkboxes are checked, uncheck them, check again and try to build again.

  4. Build Order and Project Dependencies:

    Go to ‘Solution Explorer’. Right click on Solution. Go to ‘Project Dependencies…’. You will see two tabs: ‘Dependencies’ and ‘Build Order’. This build order is the one in which solution builds. Check the project dependencies and the build order to verify if some project (say ‘project1’) which is dependent on other (say ‘project2’) is trying to build before that one (project2). This might be the cause for the error.

  5. Check the path of the missing .dll:

    Check the path of the missing .dll. If the path contains space or any other invalid path character, remove it and try building again.

    If this is the cause, then adjust the build order.

Section (2):

My particular case:

I tried all the steps above with various permutations and combinations with restarting Visual Studio a few times. But, it did not help me.

So, I decided to get rid of other error I was coming across (‘Source File Could Not Be Opened (‘Unspecified error ‘)’).

I came across a blog post: TFS Error–Source File Could Not Be Opened (‘Unspecified error ‘)

I tried the steps mentioned in that blog post, and I got rid of the error ‘Source File Could Not Be Opened (‘Unspecified error ‘)’ and surprisingly I got rid of other errors (‘metadata file could not be found’) as well.

Section (3):

Moral of the story:

Try all solutions as mentioned in section (1) above (and any other solutions) for getting rid of the error. If nothing works out, as per the blog mentioned in section (2) above, delete the entries of all source files which are no longer present in the source control and the file system from your .csproj file.


The suggested answer did not work for me. The error is a decoy for another problem.

I found out that I was targeting a slightly different version of .NET and this was flagged as a warning by the compiler, but it was causing building to fail.
This should have been flagged as an error and not a warning.