如何在程序中修改屏幕分辨率？

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;namespace ScreenResolution
{    public class Form1 : System.Windows.Forms.Form
    {
        public enum DMDO
        {
            DEFAULT = 0,
            D90 = 1,
            D180 = 2,
            D270 = 3
        }        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        struct DEVMODE
        {
            public const int DM_DISPLAYFREQUENCY = 0x400000;
            public const int DM_PELSWIDTH = 0x80000;
            public const int DM_PELSHEIGHT = 0x100000;
            private const int CCHDEVICENAME = 32;
            private const int CCHFORMNAME = 32;            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCHDEVICENAME)]
            public string dmDeviceName;
            public short dmSpecVersion;
            public short dmDriverVersion;
            public short dmSize;
            public short dmDriverExtra;
            public int dmFields;            public int dmPositionX;
            public int dmPositionY;
            public DMDO dmDisplayOrientation;
            public int dmDisplayFixedOutput;            public short dmColor;
            public short dmDuplex;
            public short dmYResolution;
            public short dmTTOption;
            public short dmCollate;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCHFORMNAME)]
            public string dmFormName;
            public short dmLogPixels;
            public int dmBitsPerPel;
            public int dmPelsWidth;
            public int dmPelsHeight;
            public int dmDisplayFlags;
            public int dmDisplayFrequency;
            public int dmICMMethod;
            public int dmICMIntent;
            public int dmMediaType;
            public int dmDitherType;
            public int dmReserved1;
            public int dmReserved2;
            public int dmPanningWidth;
            public int dmPanningHeight;
        }        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        //static extern int ChangeDisplaySettings( DEVMODE lpDevMode,  int dwFlags);        static extern int ChangeDisplaySettings([In] ref DEVMODE lpDevMode, int dwFlags);
        private System.ComponentModel.Container components = null;
        public Form1()
        {
            InitializeComponent();
        }
        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (components != null)
                {
                    components.Dispose();
                }
            }
            base.Dispose(disposing);
        }        #region Windows Form Designer generated code
        private void InitializeComponent()
        {
            this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
            this.ClientSize = new System.Drawing.Size(292, 273);
            this.Text = "改变屏幕分辨率的例子";        }
        #endregion        static void Main()
        {
            Form1 r = new Form1();
            r.ChangeRes();
            Application.Run(new Form1());
        }        void ChangeRes()
        {
            Form1 t = new Form1();
            long RetVal = 0;
            DEVMODE dm = new DEVMODE();
            dm.dmSize = (short)Marshal.SizeOf(typeof(DEVMODE));
            dm.dmPelsWidth = 1024;
            dm.dmPelsHeight = 768;
            dm.dmDisplayFrequency = 85;
            dm.dmFields = DEVMODE.DM_PELSWIDTH | DEVMODE.DM_PELSHEIGHT | DEVMODE.DM_DISPLAYFREQUENCY;
            RetVal = ChangeDisplaySettings(ref dm, 0);
        }
    }
} 这段代码，我用在了程序中，但是没有效果。请大家赐教，给出代码。