I have tried two ways of doing it :
ddlLanguage.ItemDataBound += MultiSelectDropDownItemBound;
sender, RadComboBoxItemEventArgs e)
In both ways when the page loads we will see all items checked in the dropdown. It also intelligently checks "All Items Checked" checkbox.
But am facing a problem on trying to unselect all by clicking "Check All". We have to click twice to get this working.
Is there any fix/workaround or a new property that we can set in the control itself like "AllItemsChecked = true" from server itself?