C# code to adjust screen resolution

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;
namespace 解决分辨率
{
    public partial class Form1 : Form
    {
        //保存当前屏幕分辨率
        int i = Screen.PrimaryScreen.Bounds.Width;
int j = Screen.PrimaryScreen.Bounds.Height;
        public Form1()
        {
            InitializeComponent();
        }
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        public struct DEVMODE
        {
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
            public string dmDeviceName;
            public short dmSpecVersion;
            public short dmDriverVersion;
            public short dmSize;
            public short dmDriverExtra;
            public int dmFields;
            public short dmOrientation;
            public short dmPaperSize;
            public short dmPaperLength;
            public short dmPaperWidth;
            public short dmScale;
            public short dmCopies;
            public short dmDefaultSource;
            public short dmPrintQuality;
            public short dmColor;
            public short dmDuplex;
            public short dmYResolution;
            public short dmTTOption;
            public short dmCollate;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
            public string dmFormName;
            public short dmLogPixels;
            public int dmBitsPerPel;
            public int dmPelsWidth;
            public int dmPelsHeight;
            public int dmDisplayFlags;
            public int dmDisplayFrequency;
        }
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        static extern int ChangeDisplaySettings([In] ref DEVMODE lpDevMode, int dwFlags);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        static extern bool EnumDisplaySettings(string lpszDeviceName, Int32 iModeNum, ref DEVMODE lpDevMode);
        void ChangeRes()
        {

            DEVMODE DevM = new DEVMODE();
            DevM.dmSize = (short)Marshal.SizeOf(typeof(DEVMODE));
            bool mybool;
            mybool = EnumDisplaySettings(null, 0, ref DevM);
DevM.dmPelsWidth = 1024; //Width
              DevM.dmPelsHeight = 768;                                                          
              long result = ChangeDisplaySettings(ref DevM . ;
              bool mybool; , 0, ref DevM ); DevM.dmBitsPerPel = 32;//Color Pixel
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                 private void button1_Click(object sender, EventArgs e)