A trick of operator== with NULL value in C#

public static bool operator ==(Buddy b1, Buddy b2)
{
if ((object)b2 == null && (object)b1 == null)
{
return true;
}
else if ((object)b2 != null && (object)b1 != null)
{
return (b1.Nick == b2.Nick);
}
else
return false;

}