C# 按钮控制windows音量

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;//dll引用要用到的

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, uint wParam, uint lParam);

        const uint WM_APPCOMMAND = 0x319;
        const uint APPCOMMAND_VOLUME_UP = 0x0a;
        const uint APPCOMMAND_VOLUME_DOWN = 0x09;
        const uint APPCOMMAND_VOLUME_MUTE = 0x08;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {//增加音量
            SendMessage(this.Handle, WM_APPCOMMAND, 0x30292, APPCOMMAND_VOLUME_UP * 0x10000);
        }

        private void button2_Click(object sender, EventArgs e)
        {//减少音量
            SendMessage(this.Handle, WM_APPCOMMAND, 0x30292, APPCOMMAND_VOLUME_DOWN * 0x10000);
        }

        private void button3_Click(object sender, EventArgs e)
        {//静音切换
            SendMessage(this.Handle, WM_APPCOMMAND, 0x200eb0, APPCOMMAND_VOLUME_MUTE * 0x10000);
        }

        private void button1_MouseDown(object sender, MouseEventArgs e)
        {
            
        }

    }
}