C# 下拉列表选定索引更改在更新面板中不起作用
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Drop Down List Selected Index changed not working in Update panel
提问by Mathematics
I have a drop down list in UpdatePanel_2, it gets populated when Button_1 is clicked in UpdatePanel_1.
我在 UpdatePanel_2 中有一个下拉列表，当在 UpdatePanel_1 中单击 Button_1 时，它会被填充。
My ddlist markup is,
我的 ddlist 标记是，
<asp:DropDownList id="drop1" runat="server" EnableViewState="true" AutoPostBack="true" OnSelectedIndexChanged="Drop1_SelectedIndexChanged" />
then code behind is,
那么后面的代码是，
protected void Drop1_SelectedIndexChanged(object sender, EventArgs e)
{ }
I also tried putting AutoPostback=true to my DropDownList, still no success.
我也尝试将 AutoPostback=true 放入我的 DropDownList，但仍然没有成功。
I also added triggre to update panel 2 but no gain,
我还添加了触发器来更新面板 2 但没有增益，
<Triggers>
<asp:AsyncPostbackTrigger ControlID="drop1" EventName="SelectedIndexChanged" />
</Triggers>
I am populating DropDownList using a button not PAGE LOAD METHOD PLEASE READ before answering. Thanks
我正在使用按钮而不是页面加载方法填充 DropDownList，请在回答前阅读。谢谢
采纳答案by Neeraj Dubey
Check the data to populate the DropDownListin the Page_Loadevent and always check IspostBack:
检查数据来填充DropDownList的Page_Load事件，并经常检查IspostBack：
if(!IsPostBack)
{
//DropDownList configuration
}
Use EnableViewState:
使用EnableViewState：
<asp:DropDownList ID="ddlAddDepPlans" runat="server" AutoPostBack="true" EnableViewState="true" />
Hope it helps you.
希望对你有帮助。
回答by Alberto León
Please, when you initialize it in Page_Load() check if not is postback. If you don't do it, you will always set the default value, and this replaces the value setted in the event.
请在 Page_Load() 中初始化它时检查是否不是回发。如果不这样做，您将始终设置默认值，这将替换事件中设置的值。
if(!IsPostBack)
{
//DropDownList configuration
}
回答by Jboy Flaga
I had the same issue. My problem was that the values of my ListItems were all the same :D
我遇到过同样的问题。我的问题是我的 ListItems 的值都是一样的：D
<asp:DropDownList ID="ddlFilterLogins" runat="server" Visible="true" AutoPostBack="true">
<asp:ListItem Value="0" Text="All"></asp:ListItem>
<asp:ListItem Value="0" Text="Some"></asp:ListItem>
<asp:ListItem Value="0" Text="Some more"></asp:ListItem>
</asp:DropDownList>
It should be like this:
应该是这样的：
<asp:DropDownList ID="ddlFilterLogins" runat="server" Visible="true" AutoPostBack="true">
<asp:ListItem Value="0" Text="All"></asp:ListItem>
<asp:ListItem Value="1" Text="Some"></asp:ListItem>
<asp:ListItem Value="2" Text="Some more"></asp:ListItem>
</asp:DropDownList>
Hope this helps. This might be hard to find sometimes :)
希望这可以帮助。这有时可能很难找到:)
回答by Chakri
You can use Init event instead of SelectIndexChanged. It worked fine for me. Hope you got my point.
您可以使用 Init 事件代替 SelectIndexChanged。它对我来说很好。希望你明白我的意思。
回答by Reagan
It was also a wired problem for me. finally It was because of identical listitems in the dropdown as shown below. during development you may use same items just for testing. change them.
这对我来说也是一个有线问题。最后是因为下拉列表中的列表项相同，如下所示。在开发过程中，您可以使用相同的项目进行测试。改变它们。
<asp:ListItem>Business</asp:ListItem>
<asp:ListItem>Business</asp:ListItem>
<asp:ListItem>Business</asp:ListItem>
<asp:ListItem>Business</asp:ListItem>
