Introduction - If you have any usage issues, please Google them yourself
DropDownList and ListBox controls the expansion of control: By DropDownList control and ListBox controls. Items.Add (ListItem item) method to add optgroup label, in order to achieve sub-function. The use of Method 1, set attributes: [font = Courier New] OptionGroupValue- used to add a DropDownList (ListBox) control group of the ListItem s Value value (default is [font = Courier New] optgroup) [/ font] 2, the use of DropDownList (ListBox) control. Items.Add (ListItem item) method: OptionGroupValue as the default value: [font = Courier New] SmartDropDownList.Items.Add ([font = Courier New] new ListItem ( China , optgroup )) [/ font] [/ font] [/ font]