My project can't shows windows lock screen after connected in C#

TimeSpan TS = DateTime.Now - LastEventTime;
                   if (TS.TotalMinutes   > 10) KeepMachineAwake();
                   if (!this.Sleep && this.LoggedIn)
                   {
                       BinaryFormatter bFormat = new BinaryFormatter();
                       try
                       {
                           if (this.ScreenClientX != Screen.PrimaryScreen.Bounds.Width || this.ScreenClientY != Screen.PrimaryScreen.Bounds.Height) WriteScreenSize();
                           this.SleepCount = 0;
                           SendClipboard();
                           Bitmap screeny = new Bitmap(this.ScreenServerX + this.Padding, this.ScreenServerY + this.Padding, this.ImageResoloution);
                           Graphics theShot = Graphics.FromImage(screeny);
                           Stage = "Got Screen";
                           System.Drawing.Size Sz = new System.Drawing.Size(this.ScreenServerX + this.Padding, this.ScreenServerY + this.Padding);
                           theShot.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, this.Padding, this.Padding, Sz, CopyPixelOperation.SourceCopy);
                           this.IsMetro = Helper.IsMetro(screeny);
                           if (this.Scale)//In effect we reduce the size of the image that we are sending back to the client
                               screeny = ResizeImage(screeny, this.ScreenServerX / 2, this.ScreenServerY / 2);
                           Stage = "Copy Screen";
                           int X = 0; int Y = 0;
                           Color CursorColor = WinCursor.CaptureCursor(ref X, ref Y, theShot, this.ScreenServerX, this.ScreenServerY);
                           screeny.SetPixel(0, 0, CursorColor);
                           if (this.IsMetro)
                               screeny.SetPixel(0, 1, Color.Black);
                           else
                               screeny.SetPixel(0, 1, Color.Red);
                           {
                               if (this.Encrypted)
                               {//Send as a encrypted memory stream
                                   MemoryStream MS = Encrypt(screeny);
                                   bFormat.Serialize(CStream, MS);
                               }
                               else
                                   bFormat.Serialize(CStream, screeny);
}
Stage = "Serialize Screen";
                           SleepDelay();//Pause for a bit but wake up early if the client sends a mouse click or something so we can send the desctop back early
                           theShot.Dispose();
                           screeny.Dispose();
                       }
                       catch (Exception Ex1)
                       {}