csproj copy files depending on operating system

Question

I am using .NET Core to build a cross platform class library. Depending on the operating system that the C# .NET Core project is built for using a .csproj file, I need to copy a native library to the project's output directory. E.g., for OS X I want to copy a .dylib file, for Windows I want to copy a .DLL file, for Linux I want to copy a .so file.

How can I do this with a Condition clause in a .csproj ItemGroup?

  <ItemGroup>
    <Content Include="libNative.dylib" Condition=" '$(Configuration)|$(Platform)' == 'Debug|OSX' ">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
  </ItemGroup>   

$(Platform) does not seem to work. Is there a different variable I can use?

Gavette

$(Platform) has different values, like Any CPU, x86, x64. I would check how it is done for open-source libraries with platform-specific dependencies. From what I know, some ship such platform-specific dependencies through separate nuget packages. Like they do in nuget.org/packages/CoreCompat.System.Drawing/1.0.0-beta006 – Occupier

whats the value of the $(Platform) variable when you build against OSX ? – Supersonics

Platform=AnyCPU but that's the same for Windows and Linux builds. – Gavette

The most "clean" way would be to make a NuGet package containing all native library assets in different runtime folders. when you reference such a NuGet, you get the automatic lookup for free. When integrating into the build, you need to build 3 times, once for each platform. which is okay-ish for self-contained apps, but not for portable apps. – Eleanor

@MartinUllrich Is there some example project which shows how to do that? – Gavette

Answer 1

For differentiating between Windows & Mac/Linux you can use the $(os) property: this gives you Windows_NT for Windows and UNIX for Mac/Linux.

For differentiating between Mac & Linux, at least on recent versions of MSBuild, you can use RuntimeInformation.IsOSPlatform.

So, combined, your csproj can have something like this:

<ItemGroup>
    <Content Include="libNative.dll" Condition=" '$(OS)' == 'Windows_NT' ">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
    <Content Include="libNative.so" Condition=" '$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::Linux)))' ">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
    <Content Include="libNative.dylib" Condition=" '$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::OSX)))' ">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
</ItemGroup>

To the best of my knowledge, this should work in all recent versions of .Net Core, Mono and .Net Framework.

In older versions, you'd need to resort to evil trickery for differentiating between Mac & Linux:

For Linux -> Condition=" '$(OS)' == 'Unix' and ! $([System.IO.File]::Exists('/usr/lib/libc.dylib')) "

For Mac -> Condition=" '$(OS)' == 'Unix' and $([System.IO.File]::Exists('/usr/lib/libc.dylib')) "

Sources:

• https://github.com/Microsoft/msbuild/issues/539
• https://github.com/Microsoft/msbuild/issues/2468

Luffa

Answer 2

As a follow-up to @tzachs accepted answer, since msbuild 15.3 (basically Visual Studio 2017+ or .NET Core 2+) you can shorten this to use the [MSBuild]::IsOSPlatform() method. (Documentation on this page.)

It accepts values of the OSPlatform struct, e.g. Windows, Linux, OSX, FreeBSD.

<ItemGroup>
    <Content Include="libNative.dll" Condition="$([MSBuild]::IsOSPlatform('Windows'))">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
    <Content Include="libNative.so" Condition="$([MSBuild]::IsOSPlatform('Linux'))">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
    <Content Include="libNative.dylib" Condition="$([MSBuild]::IsOSPlatform('OSX'))">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </Content>
</ItemGroup>

Stylistic

Answer 3

I did have a problem like this and ended up saving the dll in a resource and lodaing the dll for X86 or X64, when the library first initilized. It was the cleanst way for me.

Alternative when you include the dll in nuget you have also to make sure the same dll get recoped when the som one remove/clean the bin mapp.

So you have to add the file to nuger and also create a targets on build file to recopy the dll on build

Here is what i did.

internal class EmbeddedDllClass
{
    public static void LoadAllDll()
    {
        Assembly assem = Assembly.GetExecutingAssembly();
        if (IntPtr.Size == 8)
        {
            var path = Path.Combine(string.Join("\\", assem.Location.Split('\\').Reverse().Skip(1).Reverse()), "x64");

            if (!Directory.Exists(path))
                Directory.CreateDirectory(path);

            path = Path.Combine(path, "SQLite.Interop.dll");

            if (!File.Exists(path))
                File.WriteAllBytes(path, Properties.Resources.SQLite_Interop_64);
        }
        else if (IntPtr.Size == 4)
        {
            var path = Path.Combine(string.Join("\\", assem.Location.Split('\\').Reverse().Skip(1).Reverse()), "x86");

            if (!Directory.Exists(path))
                Directory.CreateDirectory(path);

            path = Path.Combine(path, "SQLite.Interop.dll");

            if (!File.Exists(path))
                File.WriteAllBytes(path, Properties.Resources.SQLite_Interop_86);

        }
    }
}

And then just call it

EmbeddedDllClass.LoadAllDll();

Ovalle

Answer 4

Wanted to create cross platform for my Nuget Package as well. Tried below code in .csproj.

<Content Include="libNative.win" Condition=" '$(OS)' == 'Windows_NT' ">
<Content Include="libNative.dylib" Condition=" '$(OS)' != 'Windows_NT' ">

So created .nupkg.

When referred the same .nupkg, on linux as the $(OS) was already set to Windows_NT, added the libNative.win and not libNative.dylib(which was expected).

So this $(OS) is set when nuget was created and not when it was added. For more details: you can use $(OS) or $(Platform) in the <Description> and see how the value is set.

Greenstone

Hello and welcome to StackOverflow! It seems your answer does not provide a solution for differenciating MacOS and Linux. Do you have any lead on this issue? – Alphosis