winforms - c# resize datagridview columns to fit control -

i have datagridview docked , anchored panel on winform. when resize form, datagridview resizes expected, columns not resize fit datagridview. instead, left background colour of datagridview.

how can columns grow control?

thanks.

private void datagrid_sizechanged(object sender, eventargs e) {     resizegridcolumns(); }  private void resizegridcolumns() {     //get sum of non-resizable columns width     int diffwidth = 0;     foreach (datagridviewcolumn col in this.datagrid.columns)     {         if (col.resizable == datagridviewtristate.false && col.visible) diffwidth += col.width;     }      //calculate available width     int totalresizablewith = this.datagrid.width - diffwidth;      //resize column width based on previous proportions     this.datagrid.columnwidthchanged -= new datagridviewcolumneventhandler(datagrid_columnwidthchanged);     (int = 0; < this.colwidthraport.count; i++)     {         try         {             if (this.datagrid.columns[i].resizable != datagridviewtristate.false && this.datagrid.columns[i].visible)             {                 this.datagrid.columns[i].width = (int)math.floor((decimal)totalresizablewith / this.colwidthraport[i]);             }         }         catch { }     }     this.datagrid.columnwidthchanged += new datagridviewcolumneventhandler(datagrid_columnwidthchanged); }  private void datagrid_columnwidthchanged(object sender, datagridviewcolumneventargs e) {     calculategridcolwidthsraport(); }  /// <summary>calculates proportions between grid width , column width</summary> private void calculategridcolwidthsraport() {     //get sum of non-resizable columns width     int diffwidth = 0;     int colwidthssum = 0;     foreach (datagridviewcolumn col in this.datagrid.columns)     {         if (col.visible)         {             colwidthssum += col.width;             if (col.resizable == datagridviewtristate.false) diffwidth += col.width;         }     }     colwidthssum += 24;      //calculate available     int totalresizablewith = colwidthssum - diffwidth;// this.datagrid.width - diffwidth;     if (this.parentform.windowstate == formwindowstate.maximized)     {         totalresizablewith = this.datagrid.width - diffwidth;     }      //calculate proportions of each column relative available width     this.colwidthraport = new list<decimal>();     foreach (datagridviewcolumn col in this.datagrid.columns)     {         this.colwidthraport.add((decimal)totalresizablewith / (decimal)col.width);     } }