间接依赖 - .NET2.0 - WMP.dll

Question

After installing Visual Studio 2017 RC, I have some code that cannot build. I have narrowed it down to WMP and .NET Framework 2 (it works under Framework 4)

The most basic test setup is 2 projects:

Project 1:

• Windows Forms App
• .NET Framework 2.0
• Namespace WMPClient
• Reference added to wmp.dll (have tried both system32 and syswow64)
• Added Windows Media Player to Form1.cs

Project 2:

• Class Library (.NET Framework)
• .NET Framework 2.0
• Namespace WMPLib
• Reference added to WMPClient

Both projects build.

When adding using WMPClient; to Class1.cs (project 2) the build fails:

13 error lines like System.Windows.Forms, mscorlib, System

warning MSB3258: The primary reference "C:\\WMPClient\\bin\\Debug\\WMPClient.exe" could not be resolved because it has an indirect dependency on the .NET Framework assembly "System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" which has a higher version "4.0.0.0" than the version "2.0.0.0" in the current target framework.

1 error line like this:

error CS0246: The type or namespace name 'WMPClient' could not be found (are you missing a using directive or an assembly reference?)

The same code does not work under VS2013 anymore either, but did before installing VS2017

Answer 1

it says your "WMPClient.exe" has a higher version 4.0 of .net framework. And by principle one cannot add higher version libraries or namespaces in a lower .NET version project. So, Either build "WMPClient.exe" with 2.0, or upgrade your Forms Project to 4.0