Overriding == operator. How to compare to null? [duplicate]

Answer 1

Cast the Person instance to object:

public static bool operator ==(Person person1, Person person2)
{
    if ((object)person1 == (object)person2) return true;
    if ((object)person1 == null) return false;
    if ((object)person2 == null) return false;
    return person1.Equals(person2);
}

Answer 2

The final (hypothetical) routine is below. It is very similar to @cdhowie's first accepted response.

public static bool operator ==(Person person1, Person person2)
{
    if (Person.ReferenceEquals(person1, person2)) return true;
    if (Person.ReferenceEquals(person1, null)) return false; //*
    return person1.Equals(person2);
}

Thanks for the great responses!

//* - .Equals() performs the null check on person2

Answer 3

Use object.ReferenceEquals(person1, null) instead of the == operator:

public static bool operator ==(Person person1, Person person2)
{
    if (object.ReferenceEquals(person1, null))
    {
         return object.ReferenceEquals(person2, null);
    }

    return person1.Equals(person2);
}