"Has invalid child element" warnings in Microsoft.Common.Targets while building

Question

In my VS2010, when I build my solution, I have over 100 warnings in the file Microsoft.Common.Targets. When I try to build, publish or run my programs, I get just the warnings, but the moment I double click it to get more info, the Microsoft.Common.Targets pops up and then I get all on the warnings.

This file Microsoft.Common.Targets is part of the .net framework and has the MSBuild in-built targets, etc. And it has the approperiate schema associated in the properties window.

Some example warnings (2 out of 100) :

Warning    2    The element 'PropertyGroup' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003' has invalid child element 'CustomBeforeMicrosoftCommonTargets' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003'. List of possible elements expected: 'Property' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003'.    C:\WINDOWS\Microsoft.NET\Framework\v3.5\Microsoft.Common.targets    22    10    Miscellaneous Files Warning    3    The element 'PropertyGroup' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003' has invalid child element '_OriginalConfiguration' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003'. List of possible elements expected: 'Property' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003'.    C:\WINDOWS\Microsoft.NET\Framework\v3.5\Microsoft.Common.targets    60    10    Miscellaneous Files 

Why is this file suddenly in my editor, when it is not part of my project, and how to tell visual studio to ignore this framework file while building.

Answer 1

If I close all the editor windows, and then build it, all the warnings have disappered! Even a close & restart of visual studio did not fix this, but just closing all files from the editor window, including Microsoft.Common.Targets, fixed the problem. Arghhh Microsoft!!

I found this out after looking at this link :

http://social.msdn.microsoft.com/Forums/en/Vsexpressvb/thread/31f52b76-b0de-406d-9c25-2f329dd7cf1c

Also works on 2013 and 2015 editions