c# - How to append text to RichTextBox without scrolling and losing selection? -

i need append text richtextbox, , need perform without making text box scroll or lose current text selection, possible?

the richtextbox in winforms quite flicker happy when play around text , select-text methods.

i have standard replacement turn off painting , scrolling following code:

class richtextboxex: richtextbox {   [dllimport("user32.dll")]   static extern intptr sendmessage(intptr hwnd, int32 wmsg, int32 wparam, ref point lparam);    [dllimport("user32.dll")]   static extern intptr sendmessage(intptr hwnd, int32 wmsg, int32 wparam, intptr lparam);    const int wm_user = 0x400;   const int wm_setredraw = 0x000b;   const int em_geteventmask = wm_user + 59;   const int em_seteventmask = wm_user + 69;   const int em_getscrollpos = wm_user + 221;   const int em_setscrollpos = wm_user + 222;    point _scrollpoint;   bool _painting = true;   intptr _eventmask;   int _suspendindex = 0;   int _suspendlength = 0;    public void suspendpainting()   {     if (_painting)     {       _suspendindex = this.selectionstart;       _suspendlength = this.selectionlength;       sendmessage(this.handle, em_getscrollpos, 0, ref _scrollpoint);       sendmessage(this.handle, wm_setredraw, 0, intptr.zero);       _eventmask = sendmessage(this.handle, em_geteventmask, 0, intptr.zero);       _painting = false;     }   }    public void resumepainting()   {     if (!_painting)     {       this.select(_suspendindex, _suspendlength);       sendmessage(this.handle, em_setscrollpos, 0, ref _scrollpoint);       sendmessage(this.handle, em_seteventmask, 0, _eventmask);       sendmessage(this.handle, wm_setredraw, 1, intptr.zero);       _painting = true;       this.invalidate();     }   } } 

and form, can happily have flicker-free richtextbox control:

richtextboxex1.suspendpainting(); richtextboxex1.appendtext("hey!"); richtextboxex1.resumepainting();