ToolsVersion="14.0"，，这个报错。

报这个错误，改个文件就ok

用VS2010打开解决方案时，输出窗口有如下提示信息：

1>Project file contains ToolsVersion="14.0". This toolset may be unknown or missing, in which case you may be able to resolve this by installing the appropriate version of MSBuild, or the build may have been forced to a particular ToolsVersion for policy reasons. Treating the project as if it had ToolsVersion="4.0". For more information, please see http://Go.microsoft.com/fwlink/?LinkId=291333.

发生此警告的原因：

原本是VS2010的项目用VS2015打开后，然后又强行转为VS2012项目。

解决方案如下：

用文本编辑器（例如Notepad++）打开VC项目（后缀名为.vcxproj），找到这一行内容：

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1. <Project DefaultTargets="Build" ToolsVersion="14.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">  

把 ToolsVersion="14.0"  改为  ToolsVersion="4.0" 即可。