I recently got caught out when writing some operator overloading code. I had originally checked if either of the objects were null in order to prevent a null reference exception not realising that the check itself was actually creating an infinite loop. Doh! Below is the correct code skeleton.

public static bool operator == (ObjectType c1,ObjectType c2)
{
    if( !(c1 is ObjectType) )
    {
        return !(c2 is ObjectType);
    }

    return c1.Equals(c2);
}

public static bool operator != (ObjectType c1, ObjectType c2)
{
    if( !(c1 is ObjectType) )
    {
        return (c2 is ObjectType);
    }

    return !c1.Equals(c2);
}


public override bool Equals(object obj)
{
    if(obj is ObjectType)
    {
        // do compare logic here
        return ((ObjectType)obj).Value == this.Value;
    }
    else
    {
        return false;
    }
}