DataList中的第二个下拉列表出错

Question

我有一个数据列表，我有两个下拉列表：第一个选择一个表，第二个选择列。到目前为止一切都很好。

当我转到datalist中的下一个项目并在Dropdownlist“ddlTable”上进行选择时，问题就出现了。执行此操作后，先前的第二个下拉列表将其值更改为第一个可能的项。你能帮我吗？我怎么能阻止它这样做？

以下是代码：

protected void Page_Load(object sender, EventArgs e)
{
    try
    {
        ScriptManager scriptManager = ScriptManager.GetCurrent(this.Page);
        if (!scriptManager.IsInAsyncPostBack && !IsPostBack)
        {
            DataList_Load(DataListItems);
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

protected void DataList_Load(int itens)
{
    try
    {
        List<int> myList = new List<int>();
        for (int i = 0; i < itens; i++)
            myList.Add(i);

        dlQuery.DataSource = myList;
        dlQuery.DataBind();

    }
    catch (Exception ex)
    {
        throw ex;
    }
}

protected void dlQuery_ItemDataBound(object sender, DataListItemEventArgs e)
{
    try
    {
        if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
        {
            var ddl = e.Item.FindControl("ddlTable") as DropDownList;
            ddlTable_Load(ddl);
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

protected void ddlTable_Load(DropDownList ddl)
{
    try
    {
        Connection cn = new Connection();
        SqlConnection SQLConn = cn.SqlLocalConn;
        SqlCommand SQLcmd = new SqlCommand("stp_Portal_GlobalMgmtQueryItens", SQLConn);
        SQLcmd.CommandType = System.Data.CommandType.StoredProcedure;

        ddl.DataSource = cn.ExecuteSqlCmd(SQLConn, SQLcmd);
        ddl.DataTextField = "name";
        ddl.DataValueField = "id";
        ddl.DataBind();
        ddl.Items.Insert(0, "Select one");
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

protected void ddlTable_SelectedIndexChanged(object sender, EventArgs e)
{
    try
    {
        DropDownList ddl1 = sender as DropDownList;
        if (ddl1.SelectedIndex > 0)
        {
            //string aux = ddl1.UniqueID;
            DropDownList ddl2 = (DropDownList)ddl1.Parent.FindControl("ddlColumn");
            //string aux2 = ddl2.UniqueID;
            ddlColumn_Load(ddl2, ddl1.SelectedValue);
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

protected void ddlColumn_Load(DropDownList ddl, string val)
{
    try
    {
        Connection cn = new Connection();
        SqlConnection SQLConn = cn.SqlLocalConn;
        SqlCommand SQLcmd = new SqlCommand("stp_Portal_GlobalMgmtQueryItemColumns", SQLConn);
        SQLcmd.CommandType = System.Data.CommandType.StoredProcedure;
        SQLcmd.Parameters.Add("@intTableId", SqlDbType.Int).Value = val;

        ddl.DataSource = cn.ExecuteSqlCmd(SQLConn, SQLcmd);
        ddl.DataTextField = "name";
        ddl.DataValueField = "id";
        ddl.DataBind();

        ddl.Items.Insert(0, "Select one");
   }
   catch (Exception ex)
   {
        throw ex;
   }
}

protected void ddlColumn_SelectedIndexChanged(object sender, EventArgs e)
{
    try
    {
        DropDownList ddl = sender as DropDownList;
        if (ddl.SelectedIndex > 0)
        {
            //just for test
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

aspx

<asp:DataList ID="dlQuery" runat="server" RepeatColumns="3" RepeatDirection="Horizontal"
    EnableViewState="true" OnItemDataBound="dlQuery_ItemDataBound">
    <ItemTemplate>
        <table>
            <tr>
                <td align="right" style="height: 20px">
                    <asp:Label ID="lblTable" runat="server" Font-Bold="true" Font-Names="Verdana" Font-Size="7pt"
                        Text="Table" ForeColor="#005780"></asp:Label>
                </td>
                <td align="left">
                    <asp:DropDownList ID="ddlTable" runat="server" AutoPostBack="True" Font-Names="Verdana"
                        Font-Size="7pt" OnSelectedIndexChanged="ddlTable_SelectedIndexChanged">
                    </asp:DropDownList>
                </td>
            </tr>
            <tr>
                <td align="right" style="height: 20px">
                    <asp:Label ID="lblColumn" runat="server" Font-Bold="true" Font-Names="Verdana" Font-Size="7pt"
                        Text="Column" ForeColor="#005780"></asp:Label>
                </td>
                <td align="left">
                    <asp:DropDownList ID="ddlColumn" runat="server" Font-Names="Verdana" Font-Size="7pt"
                        AutoPostBack="True" OnSelectedIndexChanged="ddlColumn_SelectedIndexChanged">
                    </asp:DropDownList>
                </td>
            </tr>
            <tr>
                <td align="right" style="height: 20px">
                    <asp:Label ID="lblToShow" runat="server" Font-Bold="true" Font-Names="Verdana" Font-Size="7pt"
                        Text="To Show" ForeColor="#005780"></asp:Label>
                </td>
                <td align="left">
                    <asp:CheckBox ID="cbToShow" runat="server" Font-Names="Verdana" Font-Size="7pt" />
                </td>
                <tr>
                    <td align="right" style="height: 20px">
                        <asp:Label ID="lblCrit" runat="server" Font-Bold="true" Font-Names="Verdana" Font-Size="7pt"
                            ForeColor="#005780" Text="Criteria"></asp:Label>
                    </td>
                    <td align="left">
                        <asp:TextBox ID="txtCrit" runat="server" Font-Names="Verdana" Font-Size="7pt" Width="95%"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td align="right" style="height: 20px">
                        <asp:Label ID="lblOr" runat="server" Font-Bold="true" Font-Names="Verdana" Font-Size="7pt"
                            ForeColor="#005780" Text="Or"></asp:Label>
                    </td>
                    <td align="left">
                        <asp:TextBox ID="txtOr" runat="server" Font-Names="Verdana" Font-Size="7pt" Width="95%"></asp:TextBox>
                    </td>
                </tr>
            </tr>
        </table>
    </ItemTemplate>
    <SeparatorTemplate>
        <table>
            <tr>
                <td align="right" style="width: 20px">
                </td>
            </tr>
            <tr>
                <td align="right" style="width: 20px">
                </td>
            </tr>
            <tr>
                <td align="right" style="width: 20px">
                </td>
            </tr>
            <tr>
                <td align="right" style="width: 20px">
                </td>
            </tr>
            <tr>
                <td align="right" style="width: 20px">
                </td>
            </tr>
        </table>
    </SeparatorTemplate>
</asp:DataList>