项目“ ClassLibrary1.csproj”的目标是“ netstandard2.1”。 面向'.NETFramework，Version = v4.8'的项目无法引用它

Question

I have some class library projects in targets netstandard2.1 .

When I referenced that to my WPF project in target .NET Framework v4.8 , On building time I get an error:

Severity Code Description Project File Line Suppression State Error Project '..\\ClassLibrary1\\ClassLibrary1.csproj' targets 'netstandard2.1'. It cannot be referenced by a project that targets '.NETFramework,Version=v4.8'. WpfApp1

What can I do?

Update: I read this Q/A about referencing netcoreapp2.1 and in that answer telling about add netstandar2.1 . But my libraries are already in targets netstandard2.1 !

Answer 1

What can I do?

1. If your library desn't need the very latest features, use .net standard 2.0
   in general a library should aim to support the lowest possible version.

or

2. port your WPF app to .NET Core 3 (preview)

Answer 2

According to the compatibility matrix , my NetFramework 4.8 project should not be able to reference libraries up to NetStandard 2. So the @Henk Holterman answer is true.

The versions listed here represent the rules that NuGet uses to determine whether a given .NET Standard library is applicable.

.NET Framework will not support .NET Standard 2.1 or any other later version. For more details, see this blog post .