Support multiple .NET Framework versions in your project file

When you first create a project, we recommend you create a .NET Standard class library, as it provides compatibility with the widest range of consuming projects. By using .NET Standard, you add cross-platform support to a .NET library by default. However, in some scenarios, you may also need to include code that targets a particular framework. This article shows you how to do that for SDK-style projects.

For SDK-style projects, you can configure support for multiple targets frameworks (TFM) in your project file, then use dotnet pack or msbuild /t:pack to create the package.

Note

nuget.exe CLI does not support packing SDK-style projects, so you should only use dotnet pack or msbuild /t:pack. We recommend that you include all the properties that are usually in the .nuspec file in the project file instead. To target multiple .NET Framework versions in a non-SDK-style project, see Supporting multiple .NET Framework versions.

Create a project that supports multiple .NET Framework versions

  1. Create a new .NET Standard class library either in Visual Studio or use dotnet new classlib.

    We recommend that you create a .NET Standard class library for best compatibility.

  2. Edit the .csproj file to support the target frameworks. For example, change

    <TargetFramework>netstandard2.0</TargetFramework>

    to:

    <TargetFrameworks>netstandard2.0;net45</TargetFrameworks>

    Make sure that you change the XML element changed from singular to plural (add the "s" to both the open and close tags).

  3. If you have any code that only works in one TFM, you can use #if NET45 or #if NETSTANDARD20 to separate TFM-dependent code. (For more information, see How to multitarget.) For example, you can use the following code:

    public string Platform {
       get {
    #if NET45
          return ".NET Framework"
    #elif NETSTANDARD2_0
          return ".NET Standard"
    #else
    #error This code block does not match csproj TargetFrameworks list
    #endif
       }
    }
    
  4. Add any NuGet metadata you want to the .csproj as MSBuild properties.

    For the list of available package metadata and the MSBuild property names, see pack target. Also see Controlling dependency assets.

    If you want to separate build-related properties from NuGet metadata, you can use a different PropertyGroup, or put the NuGet properties in another file and use MSBuild's Import directive to include it. Directory.Build.Props and Directory.Build.Targets are also supported starting with MSBuild 15.0.

  5. Now, use dotnet pack and the resulting .nupkg targets both .NET Standard 2.0 and .NET Framework 4.5.

Here is the .csproj file that is generated using the preceding steps and .NET Core SDK 2.2.

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>netstandard2.0;net45</TargetFrameworks>
    <Description>Sample project that targets multiple TFMs</Description>
  </PropertyGroup>

</Project>

See also