<t>I solved this problem by clearing Visual Studio Component Model Cache.<br/>
<br/>
Just delete or rename this folder: <br/>
<br/>
%LocalAppData%\Microsoft\VisualStudio\11.0\ComponentModelCache<br/>
<br/>
```<br/>
<br/>
or<br/>
<br/>
```<br/>
%LocalAppData%\Microsoft\VPDExpress\11.0\ComponentModelCache<br/>
<br/>
```<br/>
<br/>
and restart Visual Studio.<br/>
<br/>
The version of Visual Studio you have is specified by the number e.g.<br/>
<br/>
Visual Studio 2012 is `11.0` (as shown above)<br/>
<br/>
Visual Studio 2013 is `12.0`<br/>
<br/>
Visual Studio 2015 is `14.0`<br/>
<br/>
Visual Studio 2017 is `15.0`<br/>
<br/>
Visual Studio 2019 is `16.0`<br/>
<br/>
For those that don't know: <br/>
`%LocalAppData%\` is the same as `C:\Users\{yourUsername}\AppData\Local`<br/>
<br/>
For those who have multiple versions of Visual Studio installed, e.g. 2012 and 2013, it might help to remove the ComponentModelCache for both versions before restarting Visual Studio, e.g. 11.0 and 12.0.</t>
