列表框onindexchanged事件触发但是selecteditem属性为null ASP.NET

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问题描述

当ListBox1中选择了某些内容时，selectedindexchanged事件会触发，但listbox1.selecteditem / index / value为null。如何获取SelectedItem？

When something is selected in the ListBox1 the selectedindexchanged event fires however listbox1.selecteditem/index/value is null. How can I get the SelectedItem ?

   protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e)
   {
       var row = ListBox1.SelectedItem.Text;
       var date = DateTime.ParseExact(row,"yyyy-MMMM", CultureInfo.InvariantCulture);
       ChangeMonthViewOnGridView1(date.Year, date.Month);
   }


<asp:ListBox ID="ListBox1" runat="server"
OnSelectedIndexChanged="ListBox1_SelectedIndexChanged" Width="258px"
AutoPostBack="True" ></asp:ListBox>

我的尝试：

使用断点进行调试。我看不出有任何变化迹象。尝试使用下拉列表，选择项目仍然是第一个。

What I have tried:

using breaking point for debugging. I can't see no trace of signs of the change. tried with dropdownlist too there the selecteditem remains the first one.

推荐答案

<asp:ListBox ID="ListBox1" runat="server"
OnSelectedIndexChanged="ListBox1_SelectedIndexChanged" Width="258px"
AutoPostBack="True" ></asp:ListBox>

with

<asp:ListBox ID="ListBox1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ListBox1_SelectedIndexChanged">
                <asp:ListItem>2017-January</asp:ListItem>
                <asp:ListItem>2017-February</asp:ListItem>
                </asp:ListBox>

并尝试。这适用于你的代码

and try. this is working for your code behind

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