Collision detection between a circle and rectangle

[C# Programming]

I need to implement collision detection algorithm for a program i'm working on. The objects i have here is ball/circle and a rectangle. The balls are moving vertically, while the rectangle is moving horizontally. The condition is that if the ball and rectangle touch each other then an event should be raised. I have been trying to do that for a while with my colleague but without success. This is my first program in C# so please bear with me.