C# อยากทราบวิธีการ capture form โดยสามารถ SAVE มาเป็น file ภาพได้ครับ ... capture แค่ Form (หรือ Application)ที่เปิดอยุ่นะตอนนั้น

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Imaging;
using System.IO;
namespace CCapture
{
    class Program : Form
    {
        private static Bitmap bmpScreenshot;
        private static Graphics gfxScreenshot;

        static void Main(string[] args)
        {
            bmpScreenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, PixelFormat.Format32bppArgb);
            gfxScreenshot = Graphics.FromImage(bmpScreenshot);
            gfxScreenshot.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0, 0, Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);
            bmpScreenshot.Save("C:\\ThaiCreate\\Capture.jpg", ImageFormat.Jpeg);
            gfxScreenshot.Dispose();
        }
    }
}

 private void Savepic_Click(object sender, EventArgs e)
        {
    
                Rectangle form = this.Bounds;
                Bitmap bitmap = new Bitmap(form.Width, form.Height);
                Graphics graphic = Graphics.FromImage(bitmap);
                graphic.CopyFromScreen(form.Location, Point.Empty, form.Size);
                SaveFileDialog save = new SaveFileDialog();
                save.Filter = "bmpfiles|*.bmp";
                if (save.ShowDialog() == DialogResult.OK) 
                 {
                     bitmap.Save(save.FileName);
                
                 } 
            
        }

        private void checkfile()
        {
                int count, countdown;
                count = 999;
                countdown = 100;
                while (countdown <= count)
                {
                    countdown = countdown + 1;
                    if (File.Exists(Application.StartupPath + "\\MyScreenshot" + countdown + ".png"))
                    {
                    }
                    else
                    {
                        path = Application.StartupPath + "\\MyScreenshot" + countdown + ".png";
                        countdown = 1000;
                    }
                }
            }