使用方法 

ZgkeLib.ControlImage.GetPanel(panel1).Save(@"C:/1.bmp");

全部代码

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            ControlImage.GetPanel(panel1).Save("D:\\dd.gif"); ;
        }
    }
    /// <summary> 
    /// zgke@sina.com 
    /// qq:116149 
    /// Panel截图 
    /// </summary> 
    public class ControlImage
    {
        #region API
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        public struct SCROLLINFO
        {
            public uint cbSize;
            public uint fMask;
            public int nMin;
            public int nMax;
            public uint nPage;
            public int nPos;
            public int nTrackPos;
        }
        public enum ScrollBarInfoFlags
        {
            SIF_RANGE = 0x0001,
            SIF_PAGE = 0x0002,
            SIF_POS = 0x0004,
            SIF_DISABLENOSCROLL = 0x0008,
            SIF_TRACKPOS = 0x0010,
            SIF_ALL = (SIF_RANGE | SIF_PAGE | SIF_POS | SIF_TRACKPOS)
        }
        public enum ScrollBarRequests
        {
            SB_LINEUP = 0,
            SB_LINELEFT = 0,
            SB_LINEDOWN = 1,
            SB_LINERIGHT = 1,
            SB_PAGEUP = 2,
            SB_PAGELEFT = 2,
            SB_PAGEDOWN = 3,
            SB_PAGERIGHT = 3,
            SB_THUMBPOSITION = 4,
            SB_THUMBTRACK = 5,
            SB_TOP = 6,
            SB_LEFT = 6,
            SB_BOTTOM = 7,
            SB_RIGHT = 7,
            SB_ENDSCROLL = 8
        }
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int GetScrollInfo(IntPtr hwnd, int bar, ref SCROLLINFO si);
        [DllImport("user32")]
        public static extern int SetScrollPos(IntPtr hWnd, int nBar, int nPos, bool Rush);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int SendMessage(IntPtr hWnd, int msg, int wParam, int lParam);
        #endregion

        public static Bitmap GetPanel(Panel p_Panel)
        {
            bool _PanelAotu = p_Panel.AutoScroll;
            Size _PanelSize = p_Panel.Size;
            p_Panel.Visible = false;

            p_Panel.AutoScroll = true;

            MoveBar(0, 0, p_Panel);
            MoveBar(1, 0, p_Panel);
            Point _Point = GetScrollPoint(p_Panel);

            p_Panel.Width += _Point.X + 5;
            p_Panel.Height += _Point.Y + 5;

            Bitmap _BitMap = new Bitmap(p_Panel.Width, p_Panel.Height);
            p_Panel.DrawToBitmap(_BitMap, new Rectangle(0, 0, _BitMap.Width, _BitMap.Height));


            p_Panel.AutoScroll = _PanelAotu;
            p_Panel.Size = _PanelSize;

            p_Panel.Visible = true;

            return _BitMap;
        }


        /// <summary> 
        /// 获取滚动条数据 
        /// </summary> 
        /// <param name="MyControl"></param> 
        /// <param name="ScrollSize"></param> 
        /// <returns></returns> 
        private static Point GetScrollPoint(Control MyControl)
        {
            Point MaxScroll = new Point();

            SCROLLINFO ScrollInfo = new SCROLLINFO();
            ScrollInfo.cbSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(ScrollInfo);
            ScrollInfo.fMask = (uint)ScrollBarInfoFlags.SIF_ALL;

            GetScrollInfo(MyControl.Handle, 1, ref ScrollInfo);
            MaxScroll.Y = ScrollInfo.nMax - (int)ScrollInfo.nPage;
            if ((int)ScrollInfo.nPage == 0) MaxScroll.Y = 0;
            GetScrollInfo(MyControl.Handle, 0, ref ScrollInfo);
            MaxScroll.X = ScrollInfo.nMax - (int)ScrollInfo.nPage;
            if ((int)ScrollInfo.nPage == 0) MaxScroll.X = 0;
            return MaxScroll;
        }
        /// <summary> 
        /// 移动控件滚动条位置 
        /// </summary> 
        /// <param name="Bar"></param> 
        /// <param name="Point"></param> 
        /// <param name="MyControl"></param> 
        private static void MoveBar(int Bar, int Point, Control MyControl)
        {
            if (Bar == 0)
            {
                SetScrollPos(MyControl.Handle, 0, Point, true);
                SendMessage(MyControl.Handle, (int)0x0114, (int)ScrollBarRequests.SB_THUMBPOSITION, 0);
            }
            else
            {
                SetScrollPos(MyControl.Handle, 1, Point, true);
                SendMessage(MyControl.Handle, (int)0x0115, (int)ScrollBarRequests.SB_THUMBPOSITION, 0);
            }
        }
    }
}

截图效果

原窗体

图片