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我无法从 DropDownList 中获取用户选择的值。我发现我需要回发才能重置我的值并能够重新分配。（我在页面控件中尝试过诸如 ClientIDMode="static" 之类的操作并执行 "var dropDownList= $(<%= ddlNewCaseFiles.ClientID %>).val() ）但是似乎没有任何效果。所以我在我的标题：

    <script runat="server">
    protected void ddlCaseFilesNew_SelectedIndexChanged(object sender, EventArgs e)
    {
        hidNewCaseFile.Value = ddlCaseFilesNew.SelectedItem.Value;
    }
</script>

它似乎正在选择更新的值。但是由于某种原因，当我单击某个项目时，它会将我发送到“找不到资源”页面。我猜如果我在我的 DropDownList 中添加一个 Updatepanel 它可能会修复它？（因为它只是回发我的 dropDownList）。但我遇到了麻烦。

这是我的下拉列表：

<div id="ddlFiles">
        <label>
            Select new CaseFile:</label>
        <asp:DropDownList runat="server" ID="ddlCaseFilesNew" DataSourceID="dsCaseFiles"
            DataTextField="Display" DataValueField="FileID" 
            OnPreRender="ddl_PreRender" Width="300px" AutoPostBack="true" 
            onselectedindexchanged="ddlCaseFilesNew_SelectedIndexChanged"/>
    </div>

我试图在这里实现它，但我得到一个“UpdatePanel 没有名为“dropDownList”的属性名称”。任何帮助都会非常感激。：

<asp:UpdatePanel runat="server" ID="UpdatePanel1">
        <asp:DropDownList runat="server" ID="ddlCaseFilesNew" DataSourceID="dsCaseFiles"
            DataTextField="Display" DataValueField="FileID" OnPreRender="ddl_PreRender" Width="300px"
            AutoPostBack="true" onselectedindexchanged="ddlCaseFilesNew_SelectedIndexChanged" />
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="ddlCaseFilesNew" EventName="SelectedIndexChanged" />
        </Triggers>
    </asp:UpdatePanel>

按要求预渲染：

 protected void ddl_PreRender(object sender, EventArgs e)
{
    DropDownList ddl = (DropDownList)sender;
    try
    {
        if (ddl.Items[0].Value != "-1")
            ddl.Items.Insert(0, new ListItem("--Select--", "-1"));
    }
    catch
    {
        ddl.Items.Insert(0, new ListItem("--Select--", "-1"));
    }

}
4

1 回答 1

2 
if you wanna have it in the update panel 

you should add the  the hidNewCaseFile control inside ContentTemplate  tags

Example : 


 in the header 

  <script runat="server">
        protected void   DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            hidNewCaseFile.Text = ddlCaseFilesNew.SelectedItem.Value;
        }



    </script>

in the body 




    <asp:UpdatePanel ID="UpdatePanel1" runat="server">

        <ContentTemplate>

            <asp:Label runat="server" ID="hidNewCaseFile" Text="Label"></asp:Label>
            <asp:DropDownList ID="ddlCaseFilesNew" AutoPostBack="true" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
        <asp:ListItem>Uae</asp:ListItem>
        <asp:ListItem>KSA</asp:ListItem>
        <asp:ListItem>Lebanon </asp:ListItem>


    </asp:DropDownList>



        </ContentTemplate>


    </asp:UpdatePanel>

还要确保你有 <asp:ScriptManager runat="server"> </asp:ScriptManager >

在使用更新面板之前

于 2012-10-01T16:45:41.767 回答