AJAX中AutoComplete控件使用问题

     在学习AutoComplete控件的过程中,遇到了下述的问题:
 如过把参数名prefixText改成其他名称,就实现不了这个效果(特此记录)
    [WebMethod]
    public string[] GetResult(string prefixText)
    {
        //if (count == 0)
        //{
        //    count = 10;
        //}
        Random ran = new Random(DateTime.Now.Millisecond);
        List<string> result = new List<string>(10);
        for (int i = 0; i < 10; i++)
        {
            char a = (char)ran.Next(65, 78);
            char b = (char)ran.Next(97, 111);
            result.Add(prefixText + a + b);
        }
        return result.ToArray();
    }