I've multiple issues with the MultiColumn ComboBox:
1) Filtering the ComboBox with CompositeFilterDescriptor on multiple columns:
if the ComboBox is filtered and "return" is pressed, the selected/filtered values is only taken if the filter text represents the "DisplayMember" column.
So if you have 2 I (ID & NAME) and DisplayMember is NAME and ValueMember is ID and a CompositeFilter like this
you can search/filter for ID/NAME, but if you search for ID and then press "return" the item is not selected and the text becomes empty. If you do the same but search for a name the item will be selected if you press "return".
I've managed to deal with this by overriding the ProcessReturnKey function, but then there is issue #2 left:
2) Selecting a item by filtering and pressing "return" doesn't fire the SelectedIndexChanged-Event
if you have the same circumstances as 1) and you filter and then select the item by pressing "return" the SelectedIndexChanged-Event is never fired. I think this has something to do with the handling and event suppressing in "RadMultiColumnComboBoxElement.SetCurrentRowOnReturnOrTabKey". (I didn't try it, but I think the other events (like SelectedValueChanged) are neither fired.
3) Filtering/Suggesting is not working if the DropDownStyle is set to "DropDownList"
If the DropDownStyle is set to DropDownList neither the filtering nor the suggesting is working (the suggesting kinda works but with odd/strange behavior)
4) Prevent the SelectedIndexChanged event when scrolling through items
If you "scroll" through the displayed items (by keyboard) for every item the SelectedIndexChanged event is fired, makes no sense in most cases because the DropDown is still open, so is there any workaround? Or please implement the OnSelectionChangeCommitted Event.
5) MultiColumn ComboBox has a different look as the DropDownList
Using the Windows8-Theme the MultiColumn ComboBox Arrow looks different compared to the DropDownList
Also the Arrow seems a bit blurry (compared to other controls/themes)
I think there should be a uniform look across controls and themes (color / size / arrow symbol ) ...