ASP.NET - 在转发器 DataBound 上保留 DropDownList 选择

Question

Repeater 上的每个项目都有两个 DropDownLists。

我将两个列表绑定到转发器DataBound 上的两个不同列表。

两个列表都有一个OnSelectedIndexChanged 事件处理程序，它根据DropDownLists 中的选择进行一些计算。这两个列表也都有AutoPostBack="True"。

我需要立即更新计算。所以我为转发器添加了另一个数据绑定 - 在列表的事件处理程序上。

这就是问题所在 - 中继器将选择“重置”为 -1，并最终显示 DropDownLists 中的第一个项目。

如何确保数据绑定后选择仍然存在？

这是中继器结构：

            <asp:Repeater runat="server" ID="rptCart">
                <ItemTemplate>
                    <tr>
                        <td class="size"><div><asp:DropDownList runat="server" ID="_selectSize" AutoPostBack="true" OnSelectedIndexChanged="selectChange" EnableViewState="true" TabIndex="<%#Container.ItemIndex%>"></asp:DropDownList></div></td>
                        <td class="material"><div><asp:DropDownList runat="server" ID="_selectMaterial" AutoPostBack="true" OnSelectedIndexChanged="selectChange" EnableViewState="true" TabIndex="<%#Container.ItemIndex%>"></asp:DropDownList></div></td>
                    </tr>
                </ItemTemplate>
            </asp:Repeater>

还有中继器DataBound:

Protected Sub rptCart_ItemDataBound(sender As Object, e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles rptCart.ItemDataBound
    If e.Item.ItemType = ListItemType.AlternatingItem OrElse e.Item.ItemType = ListItemType.Item Then
        Dim sizeSelect As DropDownList = CType(e.Item.FindControl("_selectSize"), DropDownList)
        Dim materialSelect As DropDownList = CType(e.Item.FindControl("_selectMaterial"), DropDownList)

        sizeSelect.DataSource = sizeList
        sizeSelect.DataBind()
        materialSelect.DataSource = materialList
        materialSelect.DataBind()
    End If
End Sub

最后是DropDownLists 事件处理程序：

Protected Sub selectChange(ByVal sender As DropDownList, ByVal e As System.EventArgs)
    Dim listing As New PriceListing
    Dim ddl As DropDownList
    Dim selectedIndex As Integer

    If sender.ID = "_selectSize" Then
        For Each rptrItem As RepeaterItem In rptCart.Items
            ddl = CType(rptrItem.FindControl("_selectMaterial"), DropDownList)
            If ddl.TabIndex = sender.TabIndex Then Exit For
        Next

        For Each listing In artDecoPricing
            If listing.Size = sender.SelectedValue Then Exit For
        Next

        selectedIndex = ddl.SelectedIndex
    ElseIf sender.ID = "_selectMaterial" Then
        For Each rptrItem As RepeaterItem In rptCart.Items
            ddl = CType(rptrItem.FindControl("_selectSize"), DropDownList)
            If ddl.TabIndex = sender.TabIndex Then Exit For
        Next

        For Each listing In artDecoPricing
            If listing.Size = ddl.SelectedValue Then Exit For
        Next

        selectedIndex = sender.SelectedIndex
    End If

    Select Case selectedIndex
        Case 0
            Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Canvas
        Case 1
            Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Acrylic
        Case 2
            Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Framed
        Case 3
            Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Framed
    End Select

    Cart.SaveOrder()

    rptCart.DataSource = Cart.Order.Items
    rptCart.DataBind()
End Sub

非常感谢您！

Answer 1

您可以存储旧的选择：

Dim sizeSelect As DropDownList = CType(e.Item.FindControl("_selectSize"), DropDownList)
Dim materialSelect As DropDownList = CType(e.Item.FindControl("_selectMaterial"), DropDownList)
Dim sizeSelectedIndex = sizeSelect.SelectedIndex
Dim materialSelectedIndex = materialSelect.SelectedIndex
' do the databinding ... '
sizeSelect.SelectedIndex = If(sizeSelectedIndex < sizeSelect.Items.Count -1, sizeSelectedIndex, -1)
materialSelect.SelectedIndex = If(materialSelectedIndex < materialSelect.Items.Count -1, materialSelectedIndex, -1)