Why does String.Equals(Object obj) check to see if this == null?
- by m-y
// Determines whether two strings match.
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
public override bool Equals(Object obj)
{
//this is necessary to guard against reverse-pinvokes and
//other callers who do not use the callvirt instruction
if (this == null)
throw new NullReferenceException();
String str = obj as String;
if (str == null)
return false;
if (Object.ReferenceEquals(this, obj))
return true;
return EqualsHelper(this, str);
}
The part I don't understand is the fact that it is checking for the current instance, this, against null. The comment is a bit confusing, so I was wondering what does that comment actually mean?
Can anyone give an example of how this could break if that check was not there, and does this mean that I should also place that check in my classes?
