c# - How to restrict form movement to horizontal? -

i have standard form standard title bar user may grab , move form around. in situations want restrict movement horizontal only, no matter how mouse moves, form remains on same y coordinate.

to this, catch move event , when detect deviation y, move form original y. that:

private void templateslide_move(object sender, eventargs e) {     int y = slidesettings.lastlocation.y;     if (y != this.location.y)     {         slidesettings.lastlocation = new point(this.location.x, y);         this.location=settings.lastlocation;     } } 

but causes lot of flicker. because form moves brief moment away desired y causes other issues specific program.

is there way prevent form moving away desired y coordinate?

trap wm_moving , modify rect structure in lparam accordingly.

something like:

public partial class form1 : form {      public const int wm_moving = 0x216;      public struct rect     {         public int left;         public int top;         public int right;         public int bottom;     }      private int originaly = 0;     private int originalheight = 0;     private bool horizontalmovementonly = true;      public form1()     {         initializecomponent();         this.shown += new eventhandler(form1_shown);         this.sizechanged += new eventhandler(form1_sizechanged);         this.move += new eventhandler(form1_move);     }      void form1_move(object sender, eventargs e)     {         this.savevalues();     }      void form1_sizechanged(object sender, eventargs e)     {         this.savevalues();     }      void form1_shown(object sender, eventargs e)     {         this.savevalues();     }      private void savevalues()     {         this.originaly = this.location.y;         this.originalheight = this.size.height;     }      protected override void wndproc(ref message m)     {         switch (m.msg)         {             case wm_moving:                 if (this.horizontalmovementonly)                 {                     rect rect = (rect)system.runtime.interopservices.marshal.ptrtostructure(m.lparam, typeof(rect));                     rect.top = this.originaly;                     rect.bottom = rect.top + this.originalheight;                     system.runtime.interopservices.marshal.structuretoptr(rect, m.lparam, false);                 }                 break;         }         base.wndproc(ref m);                 } }