How to add netstandard2.0 to a C# .NET 4.5 class library

The goal today is to add netstandard2.0 support to a class library which targets full .NET 4.5

In the past, multi-targeting with portable class libraries in .net was not an easy thing to do neither it was a good support and maintenance experience. With recent updates of nuget and msbuild this has changed for good.

The library which will be converted today is RedLock. It is a c# implementation of Distributed locks with Redis. As of today the library is built with .NET 4.5 but we want to support netstandard2.0 as well. There is a table where we can see what platforms can use our netstandard2.0 library. IMO targeting 2.0 is your best choice today but it all depends on your vision ;)

Step 0 - Check if all dependencies support netstandard2.0 and .NET 4.5

Redis supports 4.5, 4.6 and netstandard15 which is great
Newtosoft JSON supports basically every platform :) NICE
LibLog is kind of 50/50. You can get it working (as described in the readme) but the installation experience is not as it was before. There is a PR which is still in progress…

Step 1 - Convert the library to netstandard2.0

This should be relatively simple task by just editing the csproj file.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
  </PropertyGroup>
  <PropertyGroup>
    <DefineConstants>TRACE;DEBUG;NETSTANDARD2_0;LIBLOG_PORTABLE;NETSTANDARD2_0</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="LibLog" Version="4.2.6" />
    <PackageReference Include="Microsoft.CSharp" Version="4.4.1" />
    <PackageReference Include="Newtonsoft.Json" Version="11.0.1" />
    <PackageReference Include="StackExchange.Redis" Version="1.2.6" />
  </ItemGroup>
</Project>

One IMPORTANT step is deleting the packages.config file. Do it :)

OK, what else. Ahh, the nuspec file is now part of the csproj file. Here it is:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
  </PropertyGroup>
  <PropertyGroup>
    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
    <PackageId>RedLock</PackageId>
    <PackageLicenseUrl>https://github.com/Elders/RedLock/blob/master/LICENSE</PackageLicenseUrl>
    <PackageProjectUrl>https://github.com/Elders/RedLock</PackageProjectUrl>
    <PackageTags>distrubited lock redis redlock cronus</PackageTags>
    <RepositoryUrl>https://github.com/Elders/RedLock</RepositoryUrl>
    <RepositoryType>Framework</RepositoryType>
    <Authors>Elders</Authors>
  </PropertyGroup>
  <PropertyGroup>
    <DefineConstants>TRACE;DEBUG;NETSTANDARD2_0;LIBLOG_PORTABLE;NETSTANDARD2_0</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="LibLog" Version="4.2.6" />
    <PackageReference Include="Microsoft.CSharp" Version="4.4.1" />
    <PackageReference Include="Newtonsoft.Json" Version="11.0.1" />
    <PackageReference Include="StackExchange.Redis" Version="1.2.6" />
  </ItemGroup>
</Project>

So far so good. We are ready with netstandard2.0 version of the RedLock library but we lost the .net45 support.

Step 2 - Add support for .NET 4.5

By modifying the TargetFrameworks we can give the compiler a hint which frameworks we want to target. In this case we want to do something like this (notice the s):

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

From now on we have to add IF statements in the csproj file to enable multiple frameworks. It goes like If the target framework is netstandard20 use the following references. In the csproj language it is:

<ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
    <PackageReference Include="LibLog" Version="4.2.6" />
    <PackageReference Include="Microsoft.CSharp" Version="4.4.1" />
    <PackageReference Include="Newtonsoft.Json" Version="11.0.1" />
    <PackageReference Include="StackExchange.Redis" Version="1.2.6" />
</ItemGroup>

You could see the relevant part for .NET 4.5 in the full csproj snippet bellow:

<Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
        <TargetFrameworks>netstandard2.0;net45</TargetFrameworks>
    </PropertyGroup>

    <!--Nuget-->
    <PropertyGroup>
        <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
        <PackageId>RedLock</PackageId>
        <PackageLicenseUrl>https://github.com/Elders/RedLock/blob/master/LICENSE</PackageLicenseUrl>
        <PackageProjectUrl>https://github.com/Elders/RedLock</PackageProjectUrl>
        <PackageTags>distrubited lock redis redlock cronus</PackageTags>
        <RepositoryUrl>https://github.com/Elders/RedLock</RepositoryUrl>
        <RepositoryType>Framework</RepositoryType>
        <Authors>Elders</Authors>
    </PropertyGroup>

    <!--netstandard2.0-->
    <PropertyGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
        <DefineConstants>TRACE;DEBUG;NETSTANDARD2_0;LIBLOG_PORTABLE</DefineConstants>
    </PropertyGroup>
    <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
        <PackageReference Include="LibLog" Version="4.2.6" />
        <PackageReference Include="Microsoft.CSharp" Version="4.4.1" />
        <PackageReference Include="Newtonsoft.Json" Version="11.0.1" />
        <PackageReference Include="StackExchange.Redis" Version="1.2.6" />
    </ItemGroup>

    <!--net45-->
    <PropertyGroup Condition="'$(TargetFramework)'=='net45'">
        <DefineConstants>TRACE;DEBUG;LIBLOG_PORTABLE</DefineConstants>
    </PropertyGroup>
    <ItemGroup Condition="'$(TargetFramework)'=='net45'">
        <Reference Include="mscorlib" />
        <Reference Include="System" />
        <Reference Include="System.Core" />
        <Reference Include="Microsoft.CSharp" />
        <PackageReference Include="StackExchange.Redis" Version="1.2.6" />
        <PackageReference Include="Newtonsoft.Json" Version="11.0.1" />
        <PackageReference Include="LibLog" Version="4.2.6" />
    </ItemGroup>
</Project>

Step 3 - Enjoy

Now we just need to compile and publish the nuget package GG

Problems with the tooling

There is one drawback and it is the tooling. I am using VisualStudio 15.5.7 and I am not able to update nuget package dependencies without editing the csproj file. Notice the nuget reference StackExchange.Redis and how it appears in two places. What will happen if there is a new version of the package and we try to update? Well, VisualStudio will update only the moniker which appears first inside TargetFrameworks and the rest have to be updated manually. In this case the version of StackExchange.Redis will be updated only inside <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">.

Here is the open issue in github.

Software is fun! Happy coding!

Written on February 19, 2018