WPF C# Tutorial

using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Media;
    class MainClass : Window
    {
        RadialGradientBrush brush;
        [STAThread]
        public static void Main()
        {
            Application app = new Application();
            app.Run(new MainClass());
        }
        public MainClass()
        {
            Title = "title";
            brush = new RadialGradientBrush(Colors.White, Colors.Red);
            brush.RadiusX = brush.RadiusY = 0.10;
            brush.SpreadMethod = GradientSpreadMethod.Repeat;
            Background = brush;
        }
        protected override void OnMouseDown(MouseButtonEventArgs args)
        {
            double width = 300;
            double height = 300;
            Point ptMouse = args.GetPosition(this);
            ptMouse.X /= width;
            ptMouse.Y /= height;
            brush.Center = ptMouse;
            brush.GradientOrigin = ptMouse;
        }
    }