Implementing Equals() for reference types is harder than it seems. My current canonical implementation goes like this:
public bool Equals( MyClass obj )
{
// If both refer to the same reference they are equal.
if( ReferenceEquals( obj, this ) )
return true;
// If the other object is null they are not equal because in C# this cannot be null.
if( ReferenceEquals( obj, null ) )
return false;
// Compare data to evaluate equality
return _data.Equals( obj._data );
}
public override bool Equals( object obj )
{
// If both refer to the same reference they are equal.
if( ReferenceEquals( obj, this ) )
return true;
// If the other object is null or is of a different types the objects are not equal.
if( ReferenceEquals( obj, null ) || obj.GetType() != GetType() )
return false;
// Use type-safe equality comparison
return Equals( (MyClass)obj );
}
public override int GetHashCode()
{
// Use data's hash code as our hashcode
return _data.GetHashCode();
}
I think that this covers all corner (inheritance and such) cases but I may be wrong. What do you guys think?