这看起来更像是一个框架问题，而不是VS / R＃问题。如果其中任何一个都无法加载描述字符串，则可能意味着缺少描述XML文件。

检查是否在以下位置看到XML文件：

C：\Program Files（x86）\ Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5.2

如果不这样做，请重新安装框架以解决问题。

链接到 .NET Framework 4.5.2开发人员包： https://www.microsoft.com/en-us/download/details.aspx?id=42637

Since a month ago, my VS doesn't seem to want to display the summary info in tooltips for any system methods or classes when I hover them with my mouse.

I had ReSharper installed and started noticing this problem. I assumed that ReSharper disabled the default method descriptions, so I wasn't thinking much further about it, only considering it a mere annoyance.

After removing ReSharper though, the problem persisted.

VS now only shows descriptions for my own methods which I've added a <summary> tag for and any descriptions from NuGet packages, but not system methods like Where, Encoding.GetString, etc.

I've tried repairing VS, resetting settings, un-/checking checkboxes in Options > Text Editor > General, but to no avail.

Has anyone had a similar problem?

This looks more like a framework issue rather that a VS/R# issue. If neither one of them can load the description strings, it probably means the description XML files are missing.

Check if you see the XML files in:

C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5.2

If you don't, then reinstall the framework to fix the issue.

Link to .NET Framework 4.5.2 Developer Pack: https://www.microsoft.com/en-us/download/details.aspx?id=42637