Why can't I compare a KeyValuePair with default

Question

In .Net 2.5 I can usually get an equality comparison (==) between a value and its type default

if (myString == default(string))

However I g

Answer 1

In order you to use the "==" equality operator on any class or struct, it needs to override the operator: http://msdn.microsoft.com/en-us/library/ms173147(v=vs.80).aspx

KeyValuePair doesn't, and therefore you get the compile error. Note, you'll get the same error if you just try this:

var k1 = new KeyValuePair();
var k2 = new KeyValuePair();

bool b = k1 == k2; //compile error

EDIT: As Eric Lippert corrected me in the comments, classes obviously don't need to override the equality operator for "==" to be valid. It'll compile fine and do a reference equality check. My mistake.