[C#] CAPTURER UNE REPRESENTATION GRAPHIQUE D'UN CONTROL

Déclaration des constantes Win32 :

Bitmap bmp = new Bitmap(this.Width, this.Height);
Graphics bmpGraphics = Graphics.FromImage(bmp);
IntPtr bmpHdc = bmpGraphics.GetHdc();
Message msg = new Message();
msg.Msg = WM_PRINT;
msg.HWnd = this.Handle;
msg.WParam = bmpHdc;
msg.LParam = new IntPtr(PRF_NONCLIENT | 
                                    PRF_CLIENT |
                                    PRF_ERASEBKGND| 
                                    PRF_CHILDREN|
                                    PRF_OWNED);
this.WndProc(ref msg);
bmpGraphics.ReleaseHdc(bmpHdc);
bmpGraphics.Dispose();

Si vous souhaitez capturer un controle particulier, il faut modifier ces lignes :

Bitmap bmp = new Bitmap(this.Width, this.Height);
msg.HWnd = this.Handle;

En remplacant this par le nom du Control voulu.
Vous pouvez ensuite utiliser la variable bmp comme bon vous semble

Dans ce Post, coq a donné une solution equivalente, mais en la mettant en forme dans une méthode toute faite, alors autant vous en faire profiter:

private const int WM_PRINT = 0x0317;
private const int PRF_CHECKVISIBLE = 0x00000001;
private const int PRF_NONCLIENT = 0x00000002;
private const int PRF_CLIENT = 0x00000004;
private const int PRF_ERASEBKGND = 0x00000008;
private const int PRF_CHILDREN = 0x00000010;
private const int PRF_OWNED = 0x00000020;

public Bitmap PrintWindowEx()
{
   Bitmap bmp = null;
   Graphics gr = null;
   IntPtr hdc = IntPtr.Zero;

   try
   {
      bmp = new Bitmap( this.ClientRectangle.Width, this.ClientRectangle.Height, this.CreateGraphics() );
      gr = Graphics.FromImage(bmp);
      hdc = gr.GetHdc();
      IntPtr wParam = hdc;
      IntPtr lParam = new IntPtr(PRF_CLIENT | PRF_CHILDREN);
      Message msg = Message.Create(this.Handle, WM_PRINT, wParam, lParam);
      this.WndProc(ref msg);
   }
catch{}
finally
{
   if ( gr != null )
   {
      if (hdc != IntPtr.Zero)
      gr.ReleaseHdc(hdc);
      gr.Dispose();
   }
}
return bmp;
}