You may be blocked from installing the .NET Core Tooling Preview 2 for Visual Studio 2015 installer due to a temporary bug. To workaround it, run the installer from the commandline with theSKIP_VSU_CHECK=1 argument, as you see in the example below.
DotNetCore.1.0.0-VS2015Tools.Preview2.exe SKIP_VSU_CHECK=1
用CMD 去安装 加SKIP_VSU_CHECK=1 参数 ok