Quote:
bool Ball::checkBallCollision(ball &ball2)
I don't think '::' is allowed in method names in C#. I assume it's something from C++.
Also, for this to even have a chance of working, I'm assuming:
1) That there's a ball class, that this code is a member of, that defines diameter and bounds as properties of the ball class.
2) That you've written you own code for SQUARE and POINT, and named them with all caps (because C# is case-sensitive and .NET code uses CamelCase for everything), as well as defined sqrt. You should really be using 'Math.Sqrt'.