The wpf application crashes when we run it on muliple monitors

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C#

WPF

Hi...
I write the following code for the maximize button because I set the windowstyle trasparent. When I press maximize button if multiple monitors are connected , the application crashes.What is the reason behind it.

IntPtr hwnd = new WindowInteropHelper(this).Handle;
               SetWindowRgn(hwnd, CreateRoundRectRgn(0, 0, (int)SystemParameters.WorkArea.Width, (int)SystemParameters.WorkArea.Height, 0, 0), true);
              this.Height = SystemParameters.WorkArea.Height;
              this.Width = SystemParameters.WorkArea.Width;
              this.Top = SystemParameters.WorkArea.Top;
              this.Left = SystemParameters.WorkArea.Left;
               if (pinFlag==false)
               {
                   LeftPanel.Width = LeftPanel.MinWidth;
               }
               flag = true;
               this.Maindocpanal.Margin = new Thickness(0,0,0,0);
               this.windowborder.CornerRadius = new CornerRadius(0);
               this.windowborder1.CornerRadius = new CornerRadius(0);

Thanks