我如何获得用户的DropDownList选择值Asp.Net（selectedIndexChange） [英] How do I get DropDownList selected value from user in Asp.Net(selectedIndexChange)

问题描述

我如何去使用的SelectedIndexChanged一个更新面板中asp.Net DropDownList中获取所选值？我试过，但是当我添加的AutoPostBack我的DropDownList，它把我送到一个错误页说，它不能找到的资源。（甚至不打我的selected_IndexChanged），我有hiddenField被分配选定的值。

下面是我的DropDownList：

 ＆LT; ASP：的ScriptManager ID =ScriptManager1=服务器/＆GT;
    ＆LT; ASP：的UpdatePanel =服务器ID =UpdatePanel1＆GT;
        ＆LT;＆的ContentTemplate GT;
            ＆LT; ASP：DropDownList的=服务器ID =ddlCaseFilesNew的DataSourceID =dsCaseFiles
                DataTextField =显示DataValueField =写到FileID在preRender =ddl_ preRenderWIDTH =300像素
                的AutoPostBack =真OnSelectedIndexChanged =ddlCaseFilesNew_SelectedIndexChanged可见=假＆GT;
                ＆LT; ASP：ListItem的＆GT;项目1 LT; / ASP：ListItem的＆GT;
            ＆LT; / ASP：DropDownList的＆GT;
        ＆LT; /＆的ContentTemplate GT;
        ＆LT;＆触发器GT;
            ＆LT; ASP：AsyncPostBackTrigger控件ID =ddlCaseFilesNew事件名称=的SelectedIndexChanged/＆GT;
        ＆LT; /触发器＆GT;
    ＆LT; / ASP：的UpdatePanel＆GT;
 

当我点击DropDownList的里面把我送到一个找不到资源页的值。我不知道为什么。它甚至没有碰我onSelectedIndexChanged

 ＆LT;脚本=服务器＆GT;
    保护无效ddlCaseFilesNew_SelectedIndexChanged（对象发件人，EventArgs的发送）
    {
        hidNewCaseFile.Value = ddlCaseFilesNew.SelectedItem.Value;
    }
＆LT; / SCRIPT＆GT;
 

解决方案

在您的SelectedIndex功能，使用

  S值的字符串=（（DropDownList的）寄件人）.SelectedValue;
 

因为它是在一个更新面板，你可能不会有通过设计师（this.DdlId）访问它。

根据在OP您的意见，这很可能是你所需要的：

 保护无效ddlCaseFilesNew_SelectedIndexChanged（对象发件人，EventArgs的发送）
{
    hidNewCaseFile.Value =（（DropDownList的）寄件人）.SelectedValue;
}
 

您还需要你的隐藏字段移动到的ContentTemplate。

How do I go about getting the selected value from the DropDownList in asp.Net using selectedIndexChanged with an update Panel? I've tried but when I add the AutoPostBack to my DropDownList, it sends me to an error page saying it cannot find the resource.(doesn't even hit my "selected_IndexChanged") I have the hiddenField being assigned the selected value.

Here is my DropDownList:

<asp:ScriptManager ID="ScriptManager1" runat="server" />
    <asp:UpdatePanel runat="server" ID="UpdatePanel1">
        <ContentTemplate>
            <asp:DropDownList runat="server" ID="ddlCaseFilesNew" DataSourceID="dsCaseFiles"
                DataTextField="Display" DataValueField="FileID" OnPreRender="ddl_PreRender" Width="300px"
                AutoPostBack="true" OnSelectedIndexChanged="ddlCaseFilesNew_SelectedIndexChanged" Visible="False">
                <asp:ListItem>Item 1</asp:ListItem>
            </asp:DropDownList>
        </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="ddlCaseFilesNew" EventName="SelectedIndexChanged" />
        </Triggers>
    </asp:UpdatePanel>

When I click on a value inside the DropDownList it sends me to a "cannot find resource" page. I have no idea why. It doesn't even touch my "onSelectedIndexChanged"

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

解决方案

In your SelectedIndex function, use

string sValue = ((DropDownList)sender).SelectedValue;

Since it's in an update panel, you likely won't have access to it via the designer (this.DdlId).

Based on your comment in the OP, this is likely what you need:

protected void ddlCaseFilesNew_SelectedIndexChanged(object sender, EventArgs e)
{
    hidNewCaseFile.Value = ((DropDownList)sender).SelectedValue;
}

You also need to move your hidden field into the ContentTemplate.

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