What exactly is the scenario that you are trying to achieve? Since you have set the ShowToggleImage to 'false', there should be no drop-down image displayed on the right side of the input area of the control. You have also set the ShowDropDownOnTextboxClick property to 'false' so no request for items will be initiated to the server since the drop-down will not open at all. You will be allowed to initiate a request to the server only if you type something in the input area.
If you, however, need to use the RadComboBox as an auto-complete control you may consider the RadAutoCompleteBox -- newly introduced RadControl for ASP.NET AJAX. The online demos for the RadAutoCompleteBox ca be found at the following link:
I hope this will help.
the Telerik team
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