记一个诡异的.net framework问题造成的系统问题（visual studio不能build或不能正常运行代码，所有基于.net framework的代码无法运行）

　　前两天碰到了一个恶心的问题：本机安装的VS2013环境突然不能Build任何程序了，Build之后就会卡住，过一段时间之后显示Build Failed。VS2010环境能Build，但是跑起来会报莫名其妙的错误。

Event Log里能查到的内容为下面两条：

Application: MSBuild.exe

Framework Version: v4.0.30319

Description: The process was terminated due to an internal error in the .NET Runtime at IP 61816AFA (61800000) with exit code 80131506.

以及

Faulting application name: MSBuild.exe, version: 12.0.40629.0, time stamp: 0x5590a5cf

Faulting module name: clr.dll, version: 4.7.2558.0, time stamp: 0x59d413ce

Exception code: 0xc0000005

Fault offset: 0x00016afa

Faulting process id: 0x6ff8

Faulting application start time: 0x01d3b0f96edd3a3d

Faulting application path: C:\Program Files (x86)\MSBuild\12.0\bin\MSBuild.exe

Faulting module path: C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll

Report Id: ac9a0144-1cec-11e8-82c1-509a4c1fef2e

Faulting package full name:

Faulting package-relative application ID:

调查了很久没有结果，后来发现甚至基于.net framework的exe程序都打不开，Event Log里的错误如下：

Application: XXX.exe

Framework Version: v4.0.30319

Description: The process was terminated due to an internal error in the .NET Runtime at IP 56656AFA (56640000) with exit code 80131506.

以及

Faulting application name: XXX.exe, version: 1.0.0.0, time stamp: 0x595a0549

Faulting module name: clr.dll, version: 4.7.2558.0, time stamp: 0x59d413ce

Exception code: 0xc0000005

Fault offset: 0x00016afa

Faulting process id: 0x83b0

Faulting application start time: 0x01d3b103cd3f886d

Faulting application path: X:\XXX\XXX\XXX.exe

Faulting module path: C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll

Report Id: 0b3083ac-1cf7-11e8-82c1-509a4c1fef2e

Faulting package full name:

Faulting package-relative application ID:

所以怀疑是.net framework的问题。根据路径想重装.net framework 4.0尝试，本机系统为Windows 8.1。但是发现了新问题：Windows 8.1下安装.net framework 4.5.1以下版本都会提示，本机已经包含了该版本，哪怕从控制面板把.net framework 4.5和4.5.1删掉也不能安装。

　　经过调查发现，.net framework 4.X向下兼容，也就是说安装4.6或者4.7能代替低版本（顺便一提，这种向下兼容只包含4.0以上，2.0和3.5不兼容），于是安装了.net framework 4.6。最终问题解决了。

　　引起问题的原因至今不明。。。希望能帮到不幸碰到类似问题的朋友们。