How can I change a .NET standard library to a .NET framework library?

If you are publishing your class library as a Nuget package then there is a better way to set this up. Check out this article:

https://weblog.west-wind.com/posts/2017/Jun/22/MultiTargeting-and-Porting-a-NET-Library-to-NET-Core-20

Basically you can setup your class library for multi targeting, allowing it to be imported into .net core projects as well as different versions of .net frameworks.

Open up the project file (.csproj) and change the TargetFramework to net462

<PropertyGroup>
  <TargetFramework>net462</TargetFramework>
</PropertyGroup>

My personal experience in Visual Studio 2017 is that recreating project and adding existent sources is the simplest, safest and most effective way - because .Net Framework based csproj file has extra xml elements (comparing with Standard based), it seems changing "TargetFramework" is not enough. Below is portion of diffs appeared by default:

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