mono/mono — pull request #491 by alanmcgovern (2012-11-01 15:50:11+00:00)
Title: [corlib] Remove the DebuggerDisplay attribute from KeyValuePair

This attribute gives us a horrible debugging experience when the
'Value' of the KeyValuePair is null. By using this attribute, the
user is told that the KeyValuePair itself is null when they inspect
something like 'new KeyValuePair (null, null)'.
This is very confusing.

We should just let the ToString method be invoked, which returns a
nicely formatted string. This is also the behaviour observed when
debugging using Visual Studio.