This sample shows how to rebind the grid.
\Syncfusion\Essential Studio\3.2.1.0\Windows\Grid.Windows\Samples\Grouping\GridGroupingRebind
To resize on a double click, you can try handling teh TableControlResizingCols event.
private void gridGroupingControl1_TableControlResizingColumns(object sender, GridTableControlResizingColumnsEventArgs e)
{
if(e.Inner.Reason == GridResizeCellsReason.DoubleClick)
{
e.TableControl.Model.ColWidths.ResizeToFit(e.Inner.Columns);
}
}