多个下拉列表具有相同的字符串值。当选择一个投放项目时，其他项目应该消失

问题描述：

<asp:DropDownList ID="DropDownList1" runat="server" Width="150px" style="padding:0" Visible="True">
        </asp:DropDownList><asp:DropDownList ID="DropDownList2" runat="server" Width="150px"  style="padding:0" Visible="True">
        </asp:DropDownList><asp:DropDownList ID="DropDownList3" runat="server" Width="150px"  style="padding:0" Visible="True">
        </asp:DropDownList>

我在下拉列表中添加项目的代码如下。但是，我想知道如何确保从下面的下拉列表中选择一个项目时，它会从其他下拉列表中消失。 我想在没有按钮的情况下这样做。我必须使用什么样的活动？非常感谢你！

My Code to add items to the dropdownlists are below. However, i wanted to know how i can make sure when one item from below dropdown is selected it dissappears from the other drop downs. I want to do this without a button. what kind of event will i have to use? THANK YOU SO MUCH IN ADVANCE!

DropDownList1.Items.Add("")
DropDownList1.Items.Add("Test1")
DropDownList1.Items.Add("Test2")
DropDownList1.Items.Add("Test3")
DropDownList1.Items.Add("Test4")
DropDownList2.Items.Add("")
DropDownList2.Items.Add("Test1")
DropDownList2.Items.Add("Test2")
DropDownList2.Items.Add("Test3")
DropDownList2.Items.Add("Test4")
DropDownList3.Items.Add("")
DropDownList3.Items.Add("Test1")
DropDownList3.Items.Add("Test2")
DropDownList3.Items.Add("Test3")
DropDownList3.Items.Add("Test4")
DropDownList4.Items.Add("")
DropDownList4.Items.Add("Test1")
DropDownList4.Items.Add("Test2")
DropDownList4.Items.Add("Test3")
DropDownList4.Items.Add("Test4")

因此，如果选择Test1来自dropdownlist1。我想让它消失在其他下拉菜单上！

谢谢你

我尝试了什么：

预渲染不起作用:(不知道该怎么办

Therefore, if "Test1" is selected from dropdownlist1. i want it to dissappear on the other dropdowns!
Thank You

What I have tried:

Pre-render didn't work :( Not sure what to do

答

以下是您的要求的示例代码，您可以根据您的要求进行修改 -

Here is a sample code for your requirement, you can modify it as per your requirement -

<asp:DropDownList ID="DropDownList1" runat="server" Width="150px" AutoPostBack="true" onselectedindexchanged="DropDownList1_SelectedIndexChanged">
        </asp:DropDownList>

        <asp:DropDownList ID="DropDownList2" runat="server" Width="150px" >
        </asp:DropDownList>

页面加载 -

on page load -

if (!IsPostBack)
       {
           DropDownList1.Items.Add("");
           DropDownList1.Items.Add("Test1");
           DropDownList1.Items.Add("Test2");
           DropDownList1.Items.Add("Test3");
           DropDownList1.Items.Add("Test4");
           DropDownList2.Items.Add("");
           DropDownList2.Items.Add("Test1");
           DropDownList2.Items.Add("Test2");
           DropDownList2.Items.Add("Test3");
           DropDownList2.Items.Add("Test4");
      }

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
               DropDownList2.Items.Remove(DropDownList2.Items.FindByValue(DropDownList1.SelectedValue));
    }

多个下拉列表具有相同的字符串值。当选择一个投放项目时，其他项目应该消失

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