Looks like after upgrading your build tool is changed from MSBUILD to Roslyn. Microsoft.Managed.Core.targets is Roslyn target file.
if you have following Nuget packages installed:
-
Microsoft.CodeDom.Providers.DotNetCompilerPlatform
-
Microsoft.Net.Compilers
Then possibly it’s causing the issue. Upgrade the Microsoft.CodeDom.Providers.DotNetCompilerPlatform
to 2.x and remove the second one. That should fix the issue.