Copying a DLL's dependencies in Visual Studio

Question

How can I set up a project in Visual Studio to copy the third-party DLLs that one of the project's references depends on?

I have a main application project and a class library DLL. The main application references the class library DLL, and the DLL itself references some third-party DLLs. When I compile the main application, it automatically copies the class library DLL to its output directory, but it does not copy the third-party DLLs.

I do not want to add references to the third-party DLLs from the main application project because the main application does not use them, they're only used by the class library.

Omnipresent

Create a post-build event that copies the DLL's, you don't need to create a project just to do that. – Unfetter

This method allows me to keep the main application's actual dependencies separate from the class library's dependencies. Too bad there's not an automatic way (that doesn't introduce psuedo references in the main application). – Omnipresent

Answer 1

You can achieve this with the project properties window. Visual Studio allows you to define events to occur, before, or after building. To get to the project properties window simply right-click on your project in the solution explorer window and click on 'properties'. From the left hand side go to the 'build events' tab.

In the post-build box type in a few copy commands. For example:

copy "$(SolutionDir)mydll.dll" "$(TargetDir)"

Where $(SolutionDir) and $(TargetDir) are both predefined variables. The standard syntax is as follows:

copy "source directory and file name" "destination directory"

If you click on the 'edit post build...' button it will bring up a box which has a listing of these predefined variables that you can insert (like $(SolutionDir) and $(TargetDir))

As a side note, this is a useful process for copying other files, such as custom configuration files, images, or any other dependencies your project may have.

Radian

Can the copy contain wildcards, as in copy SOME_DIRECTORY*.dll $(TargetDir)? – Karalynn

I have the exact same scenario as the OP but the main application project is not copying the copyd .dll files. – Aidoneus

What are the quotes for? This only works for me when removing the quotes (VS2017). – Tantalite

Answer 2

The following fragment works for me:

<Project>
  ...
  <ItemGroup>
    <Content Include="Path\to\dll\dllname.dll">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </Content>
  </ItemGroup>
  ...
</Project>

This works for C#. For native C++ it still copy dll to output folder, but this dependency is not visible in Visual Studio, it should be edited in project file directly.

To test on non-trivial example I tried to run C# project A which depends on native C++ project B. B projects depends on thirdparty native dll C - this dependency is implemented via fragment above in project file. When I build A, C is copied to binary folder.

I tried it in Visual Studio 2010.

Stepdame

This does inlcude full directory, but I need a single library. – Pragmatic

This is how I copy single file. dllname.dll is file, not a folder – Stepdame

this copies the entire directory structure to bin. like bin\Path\to\dll\dllname.dll He wants to have bin\dllname.dll – Sweettalk

@RaduSimionescu The code in the answer copies just single file. Content-element should be added for every file if multiple thirdparty dlls should be copied. And code above does not work for folders. I have not tried wildcards. Most probably I have not undestood your comment. Could you please clarify it? – Stepdame

You should add <Link>%(Filename)%(Extension)</Link> inside <Content> to avoid creating the whole directory structure and only copy the files. – Clockwise

According to MSDN you can add an optional attribute Visible=true to have the content show in the Solution Explorer. e.g. <Content Visible="true" Include="..." – Equiangular

Also, <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory> will only copy if newer and not every build. – Equiangular

Visible="true" not worked for me. I use "None" instead "Content" and in VS2017 it is visible in IDE! I placed it in the "ItemGroup" created by VS IDE using "Add Existing" (didn't check whether it matters). – Photochemistry

<Content Include="path\library.*d*"> will copy both, dll and pdb files, though it is kind of a dirty hack without future reliability... :D – Tybalt

Answer 3

Take a look at this solution provided by Alex Yakunin http://blog.alexyakunin.com/2009/09/making-msbuild-visual-studio-to.html It worked for me really nicely - the scenario being DevExpress libraries expressly used had other dependencies which caused problems when deployed)

• Note 1: Visual studio 2010 seems add referenced dlls automatically, however msbuild didn't. So Alex's solution worked since the release scripts used msbuild.
• Note 2: Also had to make sure that for the referenced libraries (those which were referenced in code) copy-local was actually set to True in the csproj, even though the Solution Explorer said it was. The best way is to set copy-local = False, Save, set copy-local = True, Save.

These two steps - copy-local=true for referenced libraries and adding msbuild targets for the indirect references automated the build setup for me.

Hagberry

File not available any more on that post – Hamel

The page is 404 now. See instead: web.archive.org/web/20180521114840/http://blog.alexyakunin.com/… – Photochemistry

Answer 4

I would not recommend doing this. You end up with an N^2 explosion in the number of assemblies being copied around (and potentially, being rebuilt). If possible, you should have all of your projects place their assemblies in the same $(OutDir). If you're using TFS, Team Build does this for you.

Gelb

Actually we do have all our assemblies being placed in one directory. My main application references them there, and when I build it copies them automatically from that directory to bin/Debug. I wanted a way for the dependecies' dependencies to get copied as well. – Omnipresent

Answer 5

I don't like to have my dependency files located in the project root folder but in a subfolder. But the files has to be placed in the root folder in the build folder.

My build events look like this:

 Command: call xcopy /S /Y "$(SolutionDir)Dependencies\*.*" "$(TargetDir)"

In case "Dependencies" also contains subfolders, as mine does.

/S means to copy subfolder also /Y means to not prompt for overwrite confirmation

Other xcopy parameters can be found at: https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/xcopy

Alanson

Answer 6

Go to the main application, references, to your class-library reference.

Set "Copy Local" to True.

It will now copy the bin directory of your class-library into the main application bin directory. Including any sub-dependency third-party dlls.

Jennelljenner

This will copy the 3rd party library into the bin directory of the class library, but not into the final output directory – Herdsman

Answer 7

If you want to copy new file only in post-build, you can also use xcopy with flags /i /d /y

xcopy "$(ProjectDir)SubDir\*.dll" "$(TargetDir)" /i /d /y

Lebkuchen

Answer 8

100% sure this will work. Just replace dll with your personal ref. file

<Reference Include="Xceed.Wpf.Toolkit">
  <HintPath>..\..\..\3rdParty\Extended WPF Toolkit-2.2.1\Xceed.Wpf.Toolkit.dll</HintPath>
   <CopyToOutputDirectory>Always</CopyToOutputDirectory>   
   <SpecificVersion>False</SpecificVersion> 
</Reference>

<Content Include="..\..\..\3rdParty\Extended WPF Toolkit-2.2.1\Xceed.Wpf.Toolkit.dll">
  <Link>Xceed.Wpf.Toolkit.dll</Link>
  <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  <SpecificVersion>False</SpecificVersion>
</Content>

Carlisle

Answer 9

I'm not really aware of any way to do this other than adding a reference to said .dll in the project itself. We've run across this in some of our own projects here, and the only solution we've found is to add the reference. I want to say that one of our developers did some research and found this to be the only solution, but don't quote me on that.

Abracadabra

we found that doing a pre or post build task was the only way to accomplish this. – Pagel