第02小程序：切换画笔

using System;

using System.Reflection;

using System.Windows.Input;

using System.Windows.Media;

namespace Chapter02

{

public class FlipThroughTheBrushes : Window

{

int index = 0;

PropertyInfo[] props;

    [STAThread]
    public static void Main()
    {
        Application app = new Application();
        app.Run(new FlipThroughTheBrushes());
    }

    public FlipThroughTheBrushes()
    {
        props = typeof(Brushes).GetProperties(BindingFlags.Public | BindingFlags.Static);
        SetTitleAndBackground();
    }

    protected override void OnKeyDown(KeyEventArgs args)
    {
        if (args.Key == Key.Down || args.Key == Key.Up)
        {
            index += args.Key == Key.Up ? 1 : props.Length - 1;
            index %= props.Length;
            SetTitleAndBackground();
        }
        base.OnKeyDown(args);
    }

    void SetTitleAndBackground()
    {
        Title = "切换画笔 - " + props[index].Name;
        Background = (Brush)props[index].GetValue(null, null);
    }
}

}