ControlVolume/ControlVolume/Pages/frmMain.cs

using ControlVolume.Views;
using System;
using System.Windows.Forms;
using ControlVolume.NativeMethods;

namespace ControlVolume
{
    public partial class frmMain : Form
    {

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

        public frmMain()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            User32.SendMessage(this.Handle, WM_APPCOMMAND, 0x30292, APPCOMMAND_VOLUME_UP * 0x10000);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            //减音量
            User32.SendMessage(this.Handle, WM_APPCOMMAND, 0x30292, APPCOMMAND_VOLUME_DOWN * 0x10000);
        }

        private void button3_Click(object sender, EventArgs e)
        {
            //静音
            User32.SendMessage(this.Handle, WM_APPCOMMAND, 0x200eb0, APPCOMMAND_VOLUME_MUTE * 0x10000);
        }

        private void button4_Click(object sender, EventArgs e)
        {
            Method2 method2 = new Method2();
            method2.Show();
        }
    }
}