We're still using TFS 2010 and it can't seem to build anything with new C# 6 syntax. I tried to follow this post to update the ToolPath property in the process template but it didn't help.
What else can I do? Install VS 2015 on the build server?
UPDATE
I realized that in the process template there is more than one "Run MSBuild for Project" place that I had to update the ToolPath property. Actually, the one I updated wasn't the right place. After I update the property at the right place the problem went away.
Also, I don't think VS2015 is needed. Just need to install Microsoft Build Tools 2015