RadComboBox fully supports checkboxes, which are displayed next
to the RadComboBoxItems. You can enable the checkboxes mode by setting the combobox's
CheckBoxes property to "True". With the checkboxes you
can 'select' multiple items. The checkbox selection is different from the standard
selection of the combobox, so there is actually no single selected item.
Both on the client and the server sides, you can use the get_checkedItems()
and CheckedItems properties to get all items, which are checked.
The Text property of the combobox holds the concatenated texts of all checked items.
The SelectedValue property is empty because there is no single selected item. You
can get the values of all checked items from the aforementioned properties.
The CheckBoxes feature provides functionality for checking all items with one checkbox.
Setting the EnableCheckAllItemsCheckBox property to "true" will
display the "Check All" section.