Question

我的ListView里面有DropDownList。我尝试了两种方法：在DropDownList和OnItemDataBound填写Page_Load。我也试过检查PostBack，但没有任何帮助。

当我试图获得价值时，我总是得到第一个。我明白这是因为列表被重新填充，但如何避免呢？如果我只在IsPostBack = false时填写它们，它们就会变空。

这是我的代码：

<asp:ListView runat="server" ID="MyListView">
    <LayoutTemplate>
        <table border="0" cellpadding="2" cellspacing="0">
            <tr>
                <th><asp:Literal runat="server" Text='<%$ Resources: Resource, LabelWhole %>' /></th>
                <th><asp:Literal runat="server" Text='<%$ Resources: Resource, LabelImport %>' /></th>
                <th><asp:Literal runat="server" Text='<%$ Resources: Resource, LabelPeriod %>' /></th>
                <th><asp:Literal runat="server" Text='<%$ Resources: Resource, LabelDate %>' /></th>
                <th><asp:Literal runat="server" Text='<%$ Resources: Resource, LabelUpload %>' /></th>
            </tr>
            <asp:PlaceHolder ID="itemPlaceholder" runat="server" />
        </table>
    </LayoutTemplate>
    <ItemTemplate>
        <tr>
            <td><%# DataBinder.Eval(Container.DataItem, "Whole") %></td>
            <td><%# DataBinder.Eval(Container.DataItem, "Upload")%></td>
            <td><%# DataBinder.Eval(Container.DataItem, "Period")%></td>
            <td><asp:DropDownList runat="server" ID="DaysDropDownList"></asp:DropDownList></td>
            <td><asp:FileUpload ID="FileUpload" runat="server" /></td>
        </tr>
    </ItemTemplate>
</asp:ListView>

foreach (var lvItem in MyListView.Items)
{
    if (lvItem.ItemType == ListViewItemType.DataItem)
    {
        DropDownList dr = lvItem.FindControl("DaysDropDownList") as DropDownList;
        for (int i = -1; i >= -12; i--)
        {
            dr.Items.Add(new ListItem(
                DateTime.Now.AddMonths(i).ToString("yyyy MM"),
                DateTime.Now.AddMonths(i).ToString("yyyy MM")));
        }
    }
}

Codebehind：

protected void Page_Load(object sender, EventArgs e)
{
    this.Application.DataLayer.LoadData(UserID);
    this.MyListView.DataSource = this.Application.DataLayer.Data;
    this.MyListView.DataBind();

    LoadDropDownLists();
}

private void LoadDropDownLists()
{
    foreach (var lvItem in MyListView.Items)
    {
        if (lvItem.ItemType == ListViewItemType.DataItem)
        {
            DropDownList dr = lvItem.FindControl("DaysDropDownList") as DropDownList;
            dr.Items.Clear();
            for (int i = -1; i >= -12; i--)
            {
                dr.Items.Add(new ListItem(
                    DateTime.Now.AddMonths(i).ToString("yyyy MM"),
                    DateTime.Now.AddMonths(i).ToString("yyyy MM")));
            }
        }
    }
}

public void SubmitButtonClick(object sender, EventArgs e)
{
    foreach (var lvItem in MyListView.Items)
    {
        if (lvItem.ItemType == ListViewItemType.DataItem)
        {
            DropDownList dr = lvItem.FindControl("DaysDropDownList") as DropDownList;
            FileUpload fl = lvItem.FindControl("FileUpload") as FileUpload;
            if (fl.HasFile)
            {
                string filename = UploadFile(fl, dr.SelectedValue);
                this.Application.DataLayer.SaveUploadRecord(UserID, 0, (int)UploadType.Upload, dr.SelectedValue, filename);
            }
        }
    }
}

Answer 1

使用ListItem填充DropdownList时，可以相应地设置ListItem的Selected属性。

Answer 2

创建一个绑定下拉列表的函数，每次页面加载时（在page_load事件中）调用此函数，但在调用之前首先清除现有的下拉列表数据源。

ListView selectedValue中的DropDownList始终是第一个

2 个答案: