autoComplete 传递第三个参数

前台代码：

<script type="text/ecmascript">
        function OnTxtKeyDown() {
            var acNameClientId = "<%=autoComplete1.BehaviorID %>";
            var acName = $find(acNameClientId);
            if (acName != null) {
                acName.set_contextKey('需要传递的参数');
            }
        }
    </script>

<asp:TextBox ID="txt" runat="server" Width="150" onkeydown="return OnTxtKeyDown();"></asp:TextBox>

<ajaxToolkit:AutoCompleteExtender runat="server" BehaviorID="AutoCompleteEx" ID="autoComplete1"
                        TargetControlID="txt" ServicePath="AutoComplete.asmx" ServiceMethod="Search"
                        MinimumPrefixLength="0" CompletionInterval="1000" EnableCaching="false" CompletionSetCount="10"
                        CompletionListCssClass="autocomplete_completionListElement" CompletionListItemCssClass="autocomplete_listItem"
                        CompletionListHighlightedItemCssClass="autocomplete_highlightedListItem" DelimiterCharacters=";, :"
                        ShowOnlyCurrentWordInCompletionListItem="true">

webservice方法：

 [WebMethod]
    public string[] GetCompletionList(string prefixText, int count,string contextKey)
    {
        if (count == 0)
        {
            count = 10;
        }

        if (prefixText.Equals("xyz"))
        {
            return new string[0];
        }

        Random random = new Random();
        List<string> items = new List<string>(count);
        for (int i = 0; i < count; i++)
        {
            char c1 = (char) random.Next(65, 90);
            char c2 = (char) random.Next(97, 122);
            char c3 = (char) random.Next(97, 122);

            items.Add(prefixText + c1 + c2 + c3);
        }

        return items.ToArray();
    }

需要注意的是第三个参数名字必须为string contextKey，否则不会进行提示；