C#

using System;
using System.Collections;
using System.Data;
using System.Drawing;
using System.Diagnostics;
using System.Windows.Forms;
using System;
using System.IO;
using System.Data;
using System.Text;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using TestMultiScroll;
 
namespace TestMultiScroll 
{
	public class Form1 : System.Windows.Forms.Form  
	{
		private System.ComponentModel.IContainer components = null;

		public System.Windows.Forms.RichTextBox RichTextBox1 = null;
		public System.Windows.Forms.RichTextBox RichTextBox2 = null;
		public System.Windows.Forms.RichTextBox RichTextBox3 = null;
  


		// ===================================================================
		//  for NativeWindow and PostMessageA
		// =================================================================== 
		private const int WM_HSCROLL = 0x114;
		private const int WM_VSCROLL = 0x115;
		private const int WM_MOUSEWHEEL = 0x20A;
		private const int WM_COMMAND = 0x111;
		// ===================================================================
		//  for GetScroll and PostMessageA
		// =================================================================== 
		private const int WM_USER = 0x400;
		private const int SBS_HORZ = 0;
		private const int SBS_VERT = 1;
		// ===================================================================
		//  for SubClassing
		// =================================================================== 
		private const int SB_THUMBPOSITION = 4;
		private Subclass  sClass1 = null;
		private Subclass  sClass2 = null;
		private Subclass  sClass3 = null;


		public Form1()
		{
			InitializeComponent();
		}
  
		protected void Dispose(bool  disposing) 
		{
			if (disposing) 
			{
				if ( !( (components ==  null))) 
				{
					components.Dispose();
				}
			}
			base.Dispose(disposing);
		}

		#region Windows Form Designer generated code
		private void InitializeComponent() 
		{
			this.RichTextBox1 =  new System.Windows.Forms.RichTextBox ();
			this.RichTextBox2 =  new System.Windows.Forms.RichTextBox ();
			this.RichTextBox3 =  new System.Windows.Forms.RichTextBox ();
			this.SuspendLayout();
			// 
			// RichTextBox1
			//  
			this.RichTextBox1.Location =  new System.Drawing.Point (24, 24);
			this.RichTextBox1.Name = "RichTextBox1";
			this.RichTextBox1.Size =  new System.Drawing.Size (128, 128);
			this.RichTextBox1.TabIndex = 0;
			this.RichTextBox1.Text = "RichTextBox1";
			this.RichTextBox1.WordWrap = false;
			// 
			// RichTextBox2
			//  
			this.RichTextBox2.Location =  new System.Drawing.Point (160, 24);
			this.RichTextBox2.Name = "RichTextBox2";
			this.RichTextBox2.Size =  new System.Drawing.Size (128, 128);
			this.RichTextBox2.TabIndex = 1;
			this.RichTextBox2.Text = "RichTextBox2";
			this.RichTextBox2.WordWrap = false;
			// 
			// RichTextBox3
			//  
			this.RichTextBox3.Location =  new System.Drawing.Point (296, 24);
			this.RichTextBox3.Name = "RichTextBox3";
			this.RichTextBox3.Size =  new System.Drawing.Size (128, 128);
			this.RichTextBox3.TabIndex = 3;
			this.RichTextBox3.Text = String.Empty;
			this.RichTextBox3.WordWrap = false;
			// 
			// Form1
			//  
			this.AutoScaleBaseSize =  new System.Drawing.Size (5, 13);
			this.ClientSize =  new System.Drawing.Size (448, 174);
			this.Controls.Add(this.RichTextBox3);
			this.Controls.Add(this.RichTextBox2);
			this.Controls.Add(this.RichTextBox1);
			this.Name = "Form1";
			this.Text = "Form1";
			this.ResumeLayout(false);
			this.Load += new System.EventHandler (Form1_Load);

			this.RichTextBox1.VScroll += new System.EventHandler (RichTextBox1_VScroll);
			this.RichTextBox2.VScroll += new System.EventHandler (RichTextBox2_VScroll);
			this.RichTextBox3.VScroll += new System.EventHandler (RichTextBox3_VScroll);
			this.RichTextBox1.HScroll += new System.EventHandler (RichTextBox1_HScroll);
			this.RichTextBox2.HScroll += new System.EventHandler (RichTextBox2_HScroll);
			this.RichTextBox3.HScroll += new System.EventHandler (RichTextBox3_HScroll);
		}
		#endregion

		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
		}

		private void Form1_Load(System.Object sender,System.EventArgs e) 
		{
			sClass1 =  new Subclass(RichTextBox1.Handle);
			sClass2 =  new Subclass(RichTextBox2.Handle);
			sClass3 =  new Subclass(RichTextBox3.Handle);
			this.sClass1.NativeWindowsEvent += new Subclass.WindowsEventHandler (sClass_WindowProcedure);
			this.sClass2.NativeWindowsEvent += new Subclass.WindowsEventHandler (sClass_WindowProcedure);
			this.sClass3.NativeWindowsEvent += new Subclass.WindowsEventHandler (sClass_WindowProcedure);

			for (int  i = 0; i <= 100; i++)
			{
				if (i % 4 == 0) 
				{
					RichTextBox1.AppendText(" this is a longer string to force HScroll " + i + System.Environment.NewLine);
					RichTextBox2.AppendText(" this is a longer string to force HScroll " + i + System.Environment.NewLine);
					RichTextBox3.AppendText(" this is a longer string to force HScroll " + i + System.Environment.NewLine);
				}
				else 
				{
					RichTextBox1.AppendText(" this is a string " + i + System.Environment.NewLine);
					RichTextBox2.AppendText(" this is a string " + i + System.Environment.NewLine);
					RichTextBox3.AppendText(" this is a string " + i + System.Environment.NewLine);
				}
			}
		}
  
		public void sClass_WindowProcedure(ref Message  uMsg) 
		{
			switch (uMsg.Msg) 
			{
				case (WM_VSCROLL):
					if (uMsg.HWnd.Equals(RichTextBox1.Handle)) 
					{
						ThumbScrollHandler(RichTextBox1, new RichTextBox[] {RichTextBox2, RichTextBox3}, ref uMsg);
					}
					if (uMsg.HWnd.Equals(RichTextBox2.Handle)) 
					{
						ThumbScrollHandler(RichTextBox2, new RichTextBox[] {RichTextBox1, RichTextBox3}, ref uMsg);
					}
					if (uMsg.HWnd.Equals(RichTextBox3.Handle)) 
					{
						ThumbScrollHandler(RichTextBox3, new RichTextBox[] {RichTextBox1, RichTextBox2}, ref uMsg);
					}
					break;
				case (WM_HSCROLL):
					if (uMsg.HWnd.Equals(RichTextBox1.Handle)) 
					{
						ThumbScrollHandler(RichTextBox1, new RichTextBox[] {RichTextBox2, RichTextBox3}, ref uMsg);
					}
					if (uMsg.HWnd.Equals(RichTextBox2.Handle)) 
					{
						ThumbScrollHandler(RichTextBox2, new RichTextBox[] {RichTextBox1, RichTextBox3}, ref uMsg);
					}
					if (uMsg.HWnd.Equals(RichTextBox3.Handle)) 
					{
						ThumbScrollHandler(RichTextBox3, new RichTextBox[] {RichTextBox1, RichTextBox2}, ref uMsg);
					}
					break;
			}
		}
  
		private void ThumbScrollHandler(RichTextBox sender, RichTextBox[] receivers, ref Message uMsg)
		{
			sClass2.NativeWindowsEvent -= new Subclass.WindowsEventHandler(ref sClass_WindowProcedure);
			foreach (RichTextBox receiver in receivers)
			{
				Message  msg = Message.Create(receiver.Handle, uMsg.Msg, uMsg.WParam, uMsg.LParam);
				sClass2.SendWndProc(ref msg);
			}
			sClass2.NativeWindowsEvent += new Subclass.WindowsEventHandler(ref sClass_WindowProcedure);
		}
		private void RichTextBox1_VScroll(object  sender,System.EventArgs e) 
		{
			VerticalScroll(RichTextBox1, new RichTextBox[2] {RichTextBox2, RichTextBox3});
		}
  
		private void RichTextBox2_VScroll(object  sender,System.EventArgs e) 
		{
			VerticalScroll(RichTextBox2, new RichTextBox[2] {RichTextBox1, RichTextBox3});
		}
  
		private void RichTextBox3_VScroll(object  sender,System.EventArgs e) 
		{
			VerticalScroll(RichTextBox3, new RichTextBox[2] {RichTextBox1, RichTextBox2});
		}
  
		private void RichTextBox1_HScroll(object  sender,System.EventArgs e) 
		{
			HorizontalScroll(RichTextBox1, new RichTextBox[2] {RichTextBox2, RichTextBox3});
		}
  
		private void RichTextBox2_HScroll(object  sender,System.EventArgs e) 
		{
			HorizontalScroll(RichTextBox2, new RichTextBox[2] {RichTextBox1, RichTextBox3});
		}
  
		private void RichTextBox3_HScroll(object  sender,System.EventArgs e) 
		{
			HorizontalScroll(RichTextBox3, new RichTextBox[2] {RichTextBox1, RichTextBox2});
		}

		private void VerticalScroll(RichTextBox sender, RichTextBox[] receivers)
		{
			int  position = GetScrollPos(sender.Handle, SBS_VERT);
			foreach (RichTextBox receiver in receivers)
			{
				PostMessageA(receiver.Handle, WM_VSCROLL, SB_THUMBPOSITION + 0x10000 * position, 0);
			}

		}
		private void HorizontalScroll(RichTextBox sender, RichTextBox[] receivers)
		{
			int  position = GetScrollPos(sender.Handle, SBS_HORZ);
			foreach(RichTextBox receiver in receivers)
			{
				PostMessageA(receiver.Handle, WM_HSCROLL, SB_THUMBPOSITION + 0x10000 * position, 0);
			}
		}
		// ===================================================================
		//  API Function: GetScrollPos()
		// =================================================================== 
		[DllImport("user32.dll")]
		private static extern int  GetScrollPos(IntPtr   hWnd, int   nBar); 
		// ===================================================================
		//  API Function: PostMessageA()
		// =================================================================== 
		[DllImport("user32.dll")]
		private static extern bool  PostMessageA(IntPtr   hwnd, int   wMsg, int   wParam, int   lParam); 
	}
 
	// ===================================================================
	//  NativeWindow Subclassing
	// =================================================================== 
	public class Subclass : System.Windows.Forms.NativeWindow  
	{
		public event WindowsEventHandler NativeWindowsEvent;
		public delegate void WindowsEventHandler(ref Message uMsg);
		public Subclass(IntPtr  pWindowHandle):base()
		{
			base.AssignHandle(pWindowHandle);
		}
		
		protected override void WndProc(ref System.Windows.Forms.Message uMsg)
		{
			base.WndProc(ref uMsg);
			if (NativeWindowsEvent != null)
				NativeWindowsEvent(ref uMsg);
		}
		
		public void SendWndProc(ref System.Windows.Forms.Message uMsg)
		{
			base.WndProc(ref uMsg);
		}
	}
}

[Serializable, StructLayout(LayoutKind.Sequential)]
private struct SYSTEMTIME 
{
  [MarshalAs(UnmanagedType.U2)] public short Year;
  [MarshalAs(UnmanagedType.U2)] public short Month;
  [MarshalAs(UnmanagedType.U2)] public short DayOfWeek;
  [MarshalAs(UnmanagedType.U2)] public short Day;
  [MarshalAs(UnmanagedType.U2)] public short Hour;
  [MarshalAs(UnmanagedType.U2)] public short Minute;
  [MarshalAs(UnmanagedType.U2)] public short Second;
  [MarshalAs(UnmanagedType.U2)] public short Milliseconds;
}

[DllImport("kernel32.dll")]
static extern bool SetSystemTime(ref SYSTEMTIME time);

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