feature evaluation disabled because a previous evaluation timed out

调试程序的时候 有些变量是IEnumerable   因为要处理大数据。

发现输入少了很多 于是跟踪debug发现 一些变量提示：

feature evaluation disabled because a previous evaluation timed out

Google了一下，解决方法list如下：

Why this is happening ?

It seems this kind of bug can happen simply when you are trying to watch at some variables who have to be thread safe but sometimes this framework implementation is not perfect....

To avoid this problem : when stepping through code where variables are bound to windows or other controls, you don't show local variables or "auto" variables. Look at such things only when you are sure your variables are all safe to look at. And note that the error doesn't necessarily appear on the unsafe variables. Use the "immediate" window on safe (i.e. non-control) variables when operating in dangerous code.

Data accessors should always be thread safe. But sometimes between two implementations (let's say between Sharepoint 2010 and Sharepoint 2012 or two version of the .NET framework), this rules is sometimes not true... There is some examples between VS2003 and 2005...

How can I increase the timeout ?

You can increase the timeout by changing the values of the registry Key HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0\Debugger using RegEdit.

Don't forget to restart Visual Studio after changing the registry key.