Question

So I have a class which overrides Equals(object obj) and GetHashCode() along with implementing IEquatable. To make working with this type a little more natural when checking for equality I thought, heck, I’d overload the equality operator and inequality operator, no worries…

Uh oh, worries… consider the following – where both myType instances are NOT null:

if (myType != container.myType) //NullReferenceException
{
    //never get here
}
//never get here either

Now, container is just another class to hold an instance of myType among other things which is used for caching items.

Here’s the actual (relevant) code from myType:

public class MyType : IEquatable<MyType>
{
    public static bool operator ==(MyType myTypeA, MyType myTypeB)
    {
        return myTypeA.Equals(myTypeB);
    }

    public static bool operator !=(MyType myTypeA, MyType myTypeB)
    {
        return !(myTypeA == myTypeB);
    }

    public override bool Equals(object obj)
    {
        if (obj != null && obj is MyType)
        {
            return Equals((MyType)obj);
        }
        return false;
    }

    public bool Equals(MyType other)
    {
        if (other != null)
        {
            return other.ToString() == ToString();
        }
        return false;
    }
}

Any experience on this front?

Thanks.

Answer 1

Tricky one… the problem is that you use the equality operator inside the Equal override as follows:

public bool Equals(MyType other)
{
    if (other != null)

It goes to your overloaded != operator, which in turn goes to your == operator, which trying to do null.Equals…