ClickOnce - File Already Exists Error - Why is a DLL File Trying to be Copied Twice by ClickOnce?

Question

Does ClickOnce only look at the application manifest file to determine which dll files to copy to the client’s machine or does it also interrogate the internals of an assembly to determine dependency files?

The reason I’m asking is because I’m getting the below ClickOnce error when trying to launch a WPF .NET 4 application that has been published with ClickOnce: The file C:\Users\CNelson\AppData\Local\Temp\Deployment\PGX6P33A.35N\AJQL8AC8.D60\tx16_rtf.dll already exists.

This error began after I’ve included a reference to two 3rd party .NET dlls that both reference an unmanaged dll file (tx16_rtf.dll). I want tx16_rtf.dll to be copied to the bin folder on the client’s PC so I have included it in my project and set the Build Action to ‘Content’ and the Copy to Output Directory to ‘Copy Always’.

However, for some reason when I try to launch the application ClickOnce is trying to copy the file ‘tx16_rtf.dll’ twice, which results in an error.

If I look at the deployment manifest file I can clearly see one and only one entry for file ‘tx16_rtf.dll’. So, my question is, why does ClickOnce try to copy file ‘tx16_rtf.dll’ twice if it only exists once in the deployment manifest file?

Below is a snippet of the deployment manifest file that references ‘tx16_rtf.dll’:

  <file name="tx16_rtf.dll" size="839680">
    <hash>
      <dsig:Transforms>
        <dsig:Transform Algorithm="urn:schemas-microsoft-com:HashTransforms.Identity" />
      </dsig:Transforms>
      <dsig:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
      <dsig:DigestValue>V6i2QcARl3+1SJHCugoazb9zrOY=</dsig:DigestValue>
    </hash>
  </file>

Answer 1

In your Visual Studio solution, how is the file added? Please try the following.

Add the dll to your project.

If you have a reference to the dll in References, set the properties on the dll like this: Build Action = none, Copy to output directory = "do not copy". Then delete the reference and then re-add the reference, but point to that dll in your local project folder. On the REference, set "copy local" to true.

If you don't have a Reference for the dll, set the properties on the dll like this: Build Action = "copy". Copy to Output Directory = "Copy always".

If you have a reference, you want the reason for it to be included to be based on the reference, and not on the dll properties. If you don't have a reference, you want to set the dll specifically to be included.

Also check the Application Files dialog and make sure the dll is not marked as Include(Prerequisite), but is Include or Include(Required).