asp.net c#将ArrayList发送到gridview不显示项目

我有3个下拉列表：

选择年份

，

选择品牌

，

选择型号

。选择模型后，结果应显示在网格视图中。我的桌子是： 使用

[（pk）MakeID，MakeName]生成带有
[（pk）ModelID、Make_ID、ModelYear、ModelName]的模型和带
[（pk）雨刮器的雨刮器，型号识别号，描述，安放位置，价格]
。当我逐步完成调试时，我看到找到了6条记录，但在gridview中没有看到

我看了这些帮助，但没有答案



我的默认值.aspx

    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">  
    </asp:ScriptManager>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
    <div id="wrapper" align="center">
    <asp:DropDownList ID="ddlYear" runat="server" 
     AutoPostBack="true" OnSelectedIndexChanged="Year_Changed">
    </asp:DropDownList>
    <asp:DropDownList ID="ddlMake" runat="server"
    AutoPostBack="true" OnSelectedIndexChanged="Make_Changed">
    </asp:DropDownList>
    <asp:DropDownList ID="ddlModel" runat="server" 
    AutoPostBack="true" 
    OnSelectedIndexChanged="Get_Wipers_By_Model">
    </asp:DropDownList>
    </div>
    </ContentTemplate>
    </asp:UpdatePanel>
    <asp:GridView ID="grdWiperList" runat="server">
    </asp:GridView>

   </form>

我的连接

public static ArrayList GetWipersByModel(string modelType)
    {
        ArrayList listResults = new ArrayList();
        string query = string.Format
        ("SELECT * FROM Wipers WHERE Model_ID LIKE '{0}'", modelType);

        try
            {
                conn.Open();
                cmd.Connection = conn;
                cmd.CommandText = query;
                SqlDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    int wiperID = reader.GetInt32(0);
                    int model_id = reader.GetInt32(1);
                    string description = reader.GetString(2);
                    string itemNo = reader.GetString(3);
                    string emplacement = reader.GetString(4);
                    decimal price = reader.GetDecimal(5);
                    Wipers wipers = new Wipers(wiperID, model_id, description, itemNo, emplacement, price);
                   listResults.Add(wipers);
                }
            }
            finally
            {
                conn.Close();
            }
        return listResults;

    }

我认为这是因为updatePanel控件试图在updatePanel控件和DropDownList控件之间添加触发器
谢谢，我注释掉了updatePanel标记，现在可以在gridview中查看记录了。我正在使用它，因为我有3个dropdownlist依赖于以前的选择，如果选择被更改，我将检查是否有回发问题。
public static ArrayList GetWipersByModel(string modelType)
    {
        ArrayList listResults = new ArrayList();
        string query = string.Format
        ("SELECT * FROM Wipers WHERE Model_ID LIKE '{0}'", modelType);

        try
            {
                conn.Open();
                cmd.Connection = conn;
                cmd.CommandText = query;
                SqlDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    int wiperID = reader.GetInt32(0);
                    int model_id = reader.GetInt32(1);
                    string description = reader.GetString(2);
                    string itemNo = reader.GetString(3);
                    string emplacement = reader.GetString(4);
                    decimal price = reader.GetDecimal(5);
                    Wipers wipers = new Wipers(wiperID, model_id, description, itemNo, emplacement, price);
                   listResults.Add(wipers);
                }
            }
            finally
            {
                conn.Close();
            }
        return listResults;

    }