Is it possible for 'this' keyword to equal null?

Question

In an example, my professor has implemented Equals as follows:

public class Person {
    private string dni;

    // ...

    public override bool Equals(object          


        

Answer 1

One way this could == null is if you practiced some black magic by overloading the == operator. For example, if someone decides that having a null or empty-string dni is equivalent to a null person:

public static bool operator ==(Person a, Person b)
{
    if(String.IsNullOrEmpty(a.dni) && (object)b == null)
        return true;

    if(String.IsNullOrEmpty(b.dni) && (object)a == null)
        return true;

    return Object.ReferenceEquals(a, b);
}

Note this is probably a Really Bad Idea.