Unable to select multiple rows on infragistics ultrawingrid with a check box column

I am having below code that successfully adds a check box column to the ultrawingrid, my problem is that when I make a selection by checking a check box on the Select column the count of selected rows of ultrawingrid is not updated and it still shows the count as zero, and also I want to know how to enable multi checkbox selection i.e multiple rows selected...

Below is the code...

private void grdPayVis_InitializeLayout(object sender,InitializeLayoutEventArgs e) 
 var gridBand = grdPayVis.DisplayLayout.Bands[0]; 
    if(!gridBand.Columns.Exists("Select"))
    gridBand.Columns.Add("Select", "Select");
gridBand.Columns["Select"].Header.VisiblePosition = 0; 
gridBand.Columns["Select"].Hidden = false; 
gridBand.Columns["Select"].Style = Infragistics.Win.UltraWinGrid.ColumnStyle.CheckBox; 
gridBand.Columns["Select"].AutoSizeMode = ColumnAutoSizeMode.AllRowsInBand; 
gridBand.Columns["Select"].CellClickAction = CellClickAction.Edit; 

}