RadCombobox Set Checkbox based on Value Selection

When a Multi Value checkbox is implemented in RadComboBox, user needs to manually click the checkbox for selection.
But one general requirement is to let the user select the item by typing and then marking the item through arrows and tab (or enter)

This can be implemented by setting OnClientSelectedIndexChanged method as follows

function ddlFilter_ItemIndexChanged(sender, e) {

    var currentitem = e.get_item();

    var isChecked = currentitem.get_checked();

    if (!isChecked) {

        //this is a user selection based on text search so set the checkbox

        currentitem.set_checked(!isChecked);

    }

}