<ajaxToolkit:AutoCompleteExtender
runat="server"
ID="autoComplete1"
TargetControlID="myTextBox"
ServiceMethod="GetCompletionList"
ServicePath="AutoComplete.asmx"
MinimumPrefixLength="2"
CompletionInterval="1000"
EnableCaching="true"
CompletionSetCount="20">
</ajaxToolkit:AutoCompleteExtender>