和以前写的Webservice在一个文件中，添加以下代码：

using System.Data.SqlClient;//需要用到ADO

...

[WebMethod]//每个需要输出的函数都要加这一句
    public String[] GetStudentInfo(String UserID)
    {
        String strConn, strSQL;
        strConn = "XXX";
        strSQL = "select XXX...\n";
        strSQL += "and pers.pers_no=@pers_no";//带参数的查询
        using (SqlConnection con = new SqlConnection(strConn))

        //SqlConnection 在 using 代码块的结尾处自动关闭
        {
            using (SqlCommand sqlcom = new SqlCommand(strSQL, con))
            {
                String pers_name = "";
                String pers_type = "";
                String dept_name = "";
                try
                {
                    con.Open();
                    sqlcom.Parameters.Add(new SqlParameter("@pers_no", UserID));
                    SqlDataReader reader = sqlcom.ExecuteReader();
                    while (reader.Read())
                    {
                        pers_name = reader.GetString(0);
                        pers_type = reader.GetString(1);
                        dept_name = reader.GetString(2);
                    }
                    reader.Close();
                    String[] s = new String[3] { pers_name, pers_type, dept_name };
                    return s;
                }
                catch (Exception ee)
                {
                    String[] s = new String[3] { ee.Message, "", "" };
                    return s;
                }
            }
        }

    }

编译后发布到本地，然后将文件夹上传到Web服务器，客户端更新一下Web引用，调用成功！