CODEWITHSUNDEEP
c#.net
Andrew Florko
Andrew Florko

Reputation: 7750

C#: best practice to overload == operator when it comes to null references

what is the best practice to overload == operator that compares two instances of the same class when it comes to null reference comparison?

MyObject o1 = null;
MyObject o2 = null;
if (o1 == o2) ... 


static bool operator == (MyClass o1, MyClass o2)
{
  // ooops! this way leads toward recursion with stackoverflow as the result
  if (o1 == null && o2 == null) 
    return true;   

  // it works!
  if (Equals(o1, null) && Equals(o2, null))
    return true;

  ... 
}

What is the best approach to handle null references in comparison ?

Upvotes: 5

Views: 1089

Answers (3)

klm_
klm_

Reputation: 1209

This is approach I follow:

http://msdn.microsoft.com/en-us/library/336aedhh.aspx

Upvotes: 2

Andrew Shepherd
Andrew Shepherd

Reputation: 45252

I've wondered if there is a "best approach". Here's how I do it:

static bool operator == (MyClass o1, MyClass o2)
{
  if(object.ReferenceEquals(o1, o2)) // This handles if they're both null
      return true;                   // or if it's the same object

  if(object.ReferenceEquals(o1, null))
      return false;

  if(object.ReferenceEquals(o2, null)) // Is this necessary? See Gabe's comment
       return false;

  return o1.Equals(o2);

}

Upvotes: 11

Itay Karo
Itay Karo

Reputation: 18286

if (ReferenceEquals(o1, null) && ReferenceEquals(o2, null))
    return true;

etc

Upvotes: 1

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