private void SliderMain_ValueChanged(object sender, RoutedPropertyChangedEventArgs <double> e) { if (DataGrid1 != null) { //MessageBox.Show(SliderMain.Value.ToString()); DataGrid1.FontSize = (int)SliderMain.Value; DataGrid1.UpdateDefaultStyle(); DataGrid1.CanUserResizeColumns = true; foreach (DataGridColumn c in DataGrid1.Columns) { c.Width = c.MinWidth; } // Update your DG's source here foreach (DataGridColumn c in DataGrid1.Columns) { c.Width = DataGridLength.Auto; } DataGrid1.RowHeight = Double.NaN; } }