Every single project I open in Visual Studio 2013 is now all of a sudden giving me the following error:
EverySingleProject.csproj : error : The default XML namespace of the project must be the MSBuild XML namespace. If the project is authored in the MSBuild 2003 format, please add xmlns="http://schemas.microsoft.com/developer/msbuild/2003" to the element. If the project has been authored in the old 1.0 or 1.2 format, please convert it to MSBuild 2003 format. C:\Program Files (x86)\MSBuild\12.0\bin\Microsoft.Common.CurrentVersion.targets
This is in the file:
Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"
Why is this failing?
Best Answer
You also get this error if you try and open a VS 2017 RC 'simplified' .NET Core csproj file in an earlier version of Visual Studio.
These new project files look like this:
(From: https://blogs.msdn.microsoft.com/dotnet/2016/12/12/updating-visual-studio-2017-rc-net-core-tooling-improvements/)
You'll need to use a recent version of VS 2017 to open them.