jQuery auto complete显示未定义的值

Question

我正在使用自动完成功能，而我正在使用undefined。此外，该函数将值返回为字符串，但在文本框值下方显示为undefined。我从过去3天开始研究这个问题，但它没有用到

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C＃

public string[] GetCompletionList(string prefixText) 
{ 
    RegistrationBAL _rbal = new RegistrationBAL(0); 
    DataSet ds = new DataSet(); 
    _rbal.LoadByContextSearch(ds, prefixText); 
    List<string> strDetailIDList = new List<string>(); 
    foreach (DataRow row in ds.Tables[0].Rows) 
    { 
         strDetailIDList.Add(row["SearchKey"].ToString()); 
    } 
    String[] s = strDetailIDList.ToArray(); return s; } 

的jQuery

<link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/themes/base/jquery-ui.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.1/jquery-ui.min.js"></script> 
<script type="text/javascript">
$(function() {
    $(".tb").autocomplete({
        source: function(request, response) {
            $.ajax({
            url: "MyService.asmx/GetCompletionList",
            data: "{ 'prefixText': '" + request.term + "' }",
                dataType: "json",
                type: "POST",
                contentType: "application/json; charset=utf-8",
                dataFilter: function(data) { return data; },
                success: function(data) {
                    response($.map(data.d, function(item) {
                        return {
                            value: item.SearchKey
                        }
                    }))
                },
                error: function(XMLHttpRequest, textStatus, errorThrown) {
                alert(textStatus);
                }
            });
        },
        minLength: 1
    });
});
</script>