You can use one of the following three methods when adding a C1AutoCompleteDataItem in the designer:

• Adding a child item through the shortcut menu
  Right-click on the C1AutoComplete control and select Add Child | AutoComplete.
  
  
• Adding a Data Item by pressing on the Add Child button
  Select C1AutoComplete control, click on the Add Child button's drop-down arrow, and select AutoComplete.
  
  
• Adding a child item through the Edit menu
  Select the C1AutoComplete control, click on the Edit menu, and select Add Child | AutoComplete.