I tried to compile my new application in MonoDevelop and I got this error:
/usr/share/dotnet/sdk/2.2.203/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.
Change the name of the file. For instance, Add prefix _ or #; so, it cannot be used.
Restart Visual Studio, then try to build. If still problem is there, needs to restart the machine.