Ensure two random shapes are never near each other or overlapping

var random = new Random();
        Canvas.SetLeft(rectangle, random.Next((int)(ImageCanvas.Width - 100)));
        Canvas.SetTop(rectangle, random.Next((int)(ImageCanvas.Height - 100)));
        return rectangle;

So the above code just randomly sets the Top and Left positions of a rectangle that will appear on the canvas. I can easily reuse this code if I want multiple rectangles to appear on the screen, however what I was having trouble doing is tweaking the code so that each rectangle is never overlapping each other.

I thought of maybe doing a while loop that keeps running random.Next((int)(ImageCanvas.Height - 100)) continuously until it is not equal to the previous random... But that isn't perfect. The shapes are quite big, so having slightly different X or Y coordinates doesn't prevent a overlap. They would somehow need to be at least 50 pixels distance between each other or something for this to prevent any overlap between other rectangles.