출처 : http://www.codeproject.com/KB/cs/take-over.aspx

using System;

using System.Windows.Forms;

using System.Runtime.InteropServices;

namespace Remo

{

/// <summary>

/// Class for Sending Mouse and Keyboard events to ANY

/// window in the system by a handle.

/// </summary>

public class TakeOver

{

private int handle;

#region SendMessage Constants

private const int WM_LBUTTONDOWN = 0x0201;

private const int WM_LBUTTONUP = 0x0202;

private const int WM_LBUTTONDBLCLK = 0x0203;

private const int WM_RBUTTONDOWN = 0x0204;

private const int WM_RBUTTONUP = 0x0205;

private const int WM_RBUTTONDBLCLK = 0x0206;

private const int WM_MOUSEMOVE = 0x0200;

private const int WM_KEYDOWN = 0x100;

private const int WM_KEYUP = 0x0101;

private const int WM_CHAR = 0x0102;

#endregion SendMessage Constants

#region Virtual Keys Constants

public const int VK_0 = 0x30;

public const int VK_1 = 0x31;

public const int VK_2 = 0x32;

public const int VK_3 = 0x33;

public const int VK_4 = 0x34;

public const int VK_5 = 0x35;

public const int VK_6 = 0x36;

public const int VK_7 = 0x37;

public const int VK_8 = 0x38;

public const int VK_9 = 0x39;

public const int VK_A = 0x41;

public const int VK_B = 0x42;

public const int VK_C = 0x43;

public const int VK_D = 0x44;

public const int VK_E = 0x45;

public const int VK_F = 0x46;

public const int VK_G = 0x47;

public const int VK_H = 0x48;

public const int VK_I = 0x49;

public const int VK_J = 0x4A;

public const int VK_K = 0x4B;

public const int VK_L = 0x4C;

public const int VK_M = 0x4D;

public const int VK_N = 0x4E;

public const int VK_O = 0x4F;

public const int VK_P = 0x50;

public const int VK_Q = 0x51;

public const int VK_R = 0x52;

public const int VK_S = 0x53;

public const int VK_T = 0x54;

public const int VK_U = 0x55;

public const int VK_V = 0x56;

public const int VK_W = 0x57;

public const int VK_X = 0x58;

public const int VK_Y = 0x59;

public const int VK_Z = 0x5A;

public const int VK_BACK = 0x08;

public const int VK_TAB = 0x09;

public const int VK_CLEAR = 0x0C;

public const int VK_RETURN = 0x0D;

public const int VK_SHIFT = 0x10;

public const int VK_CONTROL = 0x11;

public const int VK_MENU = 0x12;

public const int VK_PAUSE = 0x13;

public const int VK_CAPITAL = 0x14;

public const int VK_KANA = 0x15;

public const int VK_HANGEUL = 0x15;

public const int VK_HANGUL = 0x15;

public const int VK_JUNJA = 0x17;

public const int VK_FINAL = 0x18;

public const int VK_HANJA = 0x19;

public const int VK_KANJI = 0x19;

public const int VK_ESCAPE = 0x1B;

public const int VK_CONVERT = 0x1C;

public const int VK_NONCONVERT= 0x1D;

public const int VK_ACCEPT = 0x1E;

public const int VK_MODECHANGE= 0x1F;

public const int VK_SPACE = 0x20;

public const int VK_PRIOR = 0x21;

public const int VK_NEXT = 0x22;

public const int VK_END = 0x23;

public const int VK_HOME = 0x24;

public const int VK_LEFT = 0x25;

public const int VK_UP = 0x26;

public const int VK_RIGHT = 0x27;

public const int VK_DOWN = 0x28;

public const int VK_SELECT = 0x29;

public const int VK_PRINT = 0x2A;

public const int VK_EXECUTE = 0x2B;

public const int VK_SNAPSHOT = 0x2C;

public const int VK_INSERT = 0x2D;

public const int VK_DELETE = 0x2E;

public const int VK_HELP = 0x2F;

public const int VK_LWIN = 0x5B;

public const int VK_RWIN = 0x5C;

public const int VK_APPS = 0x5D;

public const int VK_SLEEP = 0x5F;

public const int VK_NUMPAD0 = 0x60;

public const int VK_NUMPAD1 = 0x61;

public const int VK_NUMPAD2 = 0x62;

public const int VK_NUMPAD3 = 0x63;

public const int VK_NUMPAD4 = 0x64;

public const int VK_NUMPAD5 = 0x65;

public const int VK_NUMPAD6 = 0x66;

public const int VK_NUMPAD7 = 0x67;

public const int VK_NUMPAD8 = 0x68;

public const int VK_NUMPAD9 = 0x69;

public const int VK_MULTIPLY = 0x6A;

public const int VK_ADD = 0x6B;

public const int VK_SEPARATOR = 0x6C;

public const int VK_SUBTRACT = 0x6D;

public const int VK_DECIMAL = 0x6E;

public const int VK_DIVIDE = 0x6F;

public const int VK_F1 = 0x70;

public const int VK_F2 = 0x71;

public const int VK_F3 = 0x72;

public const int VK_F4 = 0x73;

public const int VK_F5 = 0x74;

public const int VK_F6 = 0x75;

public const int VK_F7 = 0x76;

public const int VK_F8 = 0x77;

public const int VK_F9 = 0x78;

public const int VK_F10 = 0x79;

public const int VK_F11 = 0x7A;

public const int VK_F12 = 0x7B;

public const int VK_F13 = 0x7C;

public const int VK_F14 = 0x7D;

public const int VK_F15 = 0x7E;

public const int VK_F16 = 0x7F;

public const int VK_F17 = 0x80;

public const int VK_F18 = 0x81;

public const int VK_F19 = 0x82;

public const int VK_F20 = 0x83;

public const int VK_F21 = 0x84;

public const int VK_F22 = 0x85;

public const int VK_F23 = 0x86;

public const int VK_F24 = 0x87;

public const int VK_NUMLOCK = 0x90;

public const int VK_SCROLL = 0x91;

#endregion Virtual Keys Constants

[DllImport("user32.dll", CharSet=CharSet.Auto)]

private static extern int SendMessage(int hWnd, int msg, int wParam, IntPtr lParam);

[DllImport("user32.dll", CharSet=CharSet.Auto)] // used for button-down & button-up

private static extern int PostMessage(int hWnd, int msg, int wParam, IntPtr lParam);

[DllImport("user32.dll", CharSet=CharSet.Auto)]

private static extern bool SetForegroundWindow(IntPtr hWnd);

public TakeOver(int handle)

{

this.handle = handle;

}

public void SetFocus()

{

SetForegroundWindow(new IntPtr(this.handle));

}

public void SendLeftButtonDown(int x,int y)

{

PostMessage(handle,WM_LBUTTONDOWN,0,new IntPtr(y * 0x10000 + x));

}

public void SendLeftButtonUp(int x,int y)

{

PostMessage(handle,WM_LBUTTONUP,0,new IntPtr(y * 0x10000 + x));

}

public void SendLeftButtonDblClick(int x,int y)

{

PostMessage(handle,WM_LBUTTONDBLCLK,0,new IntPtr(y * 0x10000 + x));

}

public void SendRightButtonDown(int x,int y)

{

PostMessage(handle,WM_RBUTTONDOWN,0,new IntPtr(y * 0x10000 + x));

}

public void SendRightButtonUp(int x,int y)

{

PostMessage(handle,WM_RBUTTONUP,0,new IntPtr(y * 0x10000 + x));

}

public void SendRightButtonDblClick(int x,int y)

{

PostMessage(handle,WM_RBUTTONDBLCLK,0,new IntPtr(y * 0x10000 + x));

}

public void SendMouseMove(int x,int y)

{

PostMessage(handle,WM_MOUSEMOVE,0,new IntPtr(y * 0x10000 + x));

}

public void SendKeyDown(int key)

{

PostMessage(handle,WM_KEYDOWN,key,IntPtr.Zero);

}

public void SendKeyUp(int key)

{

PostMessage(handle,WM_KEYUP,key,new IntPtr(1));

}

public void SendChar(char c)

{

SendMessage(handle, WM_CHAR, c, IntPtr.Zero);

}

public void SendString(string s)

{

foreach (char c in s) SendChar(c);

}

}

}

C# PostMessage API