Visual studio2015 can't open project

[hanjunjun]

Error content： The project's default XML namespace must be the MSBuild XML namespace. If the project was created in MSBuild 2003 format, add xmlns="http://schemas.microsoft.com/developer/msbuild/2003" to the <Project> element. If the project was created in the old 1.0 or 1.2 format, convert it to MSBuild 2003 format.

What should I do to successfully compile the project?

[yfakariya]

If you can, use visual studio 2017 to open solutions except MsgPack.Windows.sln which contains Silverlight 5 project.

AFAIK, VS 2015 does not support "SDK-based" projects. I don't want to back old and troublesome project.json based projects...

[hanjunjun]

Is there any way to open the project with vs2015?

[yfakariya]

Unfortunately, I don't know how to do it. If you want to study or contribute OSS, you can use Visual Studio Community even if you belong a "big" company (of course, you should read its license terms carefully).