WinForm go down except MDI form border

In the middle of the project encountered an MDI window inside the border problem, after hard to find, and finally got the solution

Calling the API in the main form

  //Win32 Constants        Private Const intGwl_style =- -; Private Const intGwl_exstyle =- -; Private Const intWs_border =0x00800000; Private Const intWs_ex_clientedge =0x00000200; Private Const UINTSwp_nosize =0x0001; Private Const UINTSwp_nomove =0x0002; Private Const UINTSwp_nozorder =0x0004; Private Const UINTSwp_noactivate =0x0010; Private Const UINTSwp_framechanged =0x0020; Private Const UINTSwp_noownerzorder =0x0200; //Win32 Method[DllImport ("user32.dll", CharSet =CharSet.Auto)]Private Static extern intGetWindowLong (IntPtr hWnd,intIndex); [DllImport ("user32.dll", CharSet =CharSet.Auto)]Private Static extern intSetWindowLong (IntPtr hWnd,intIndex,intValue); [DllImport ("user32.dll", exactspelling =true)]        Private Static extern intSetWindowPos (IntPtr hWnd, IntPtr hwndinsertafter,intXintYintCxintCyUINTUflags);


Add the following code to the Form_Load event after getting to the API

  //get MDI client area             for(inti =0; I < This. Controls.Count; i++)            {                varMdiclientform = This. Controls[i] asmdiclient; if(Mdiclientform = =NULL)Continue; //MDI client area found//get border of customer area                intstyle =GetWindowLong (Mdiclientform.handle, Gwl_style); intExStyle =GetWindowLong (Mdiclientform.handle, Gwl_exstyle); Style&= ~Ws_border; ExStyle&= ~Ws_ex_clientedge; //call Win32 to set styleSetWindowLong (Mdiclientform.handle, Gwl_style, STYLE);                SetWindowLong (Mdiclientform.handle, Gwl_exstyle, ExStyle); //Update Customer AreaSetWindowPos (Mdiclientform.handle, IntPtr.Zero,0,0,0,0, Swp_noactivate| Swp_nomove | Swp_nosize | Swp_nozorder |Swp_noownerzorder|swp_framechanged);                UpdateStyles ();  Break; }

Re-run the program, OK

WinForm go down except MDI form border