下拉列表AJAX的SelectedIndexChanged事件 [英] SelectedIndexChanged Event for Dropdownlist AJAX

问题描述

你好，

感谢您的阅读.这是我的情况.我有一个UpdatePanel，并且里面有2个下拉列表.我只想在dropdownlist1中选择特定值时显示第二个ddlist.我在selectedIndexChanged事件上使用了Javascript/label等，但仍然无法正常工作.事件被触发，我顺利通过代码，但它没有在屏幕上呈现.下面的代码段.所有的帮助都非常，感谢和感激.

前端

Hello,

Thank you for reading. Here is my situation. I have an UpdatePanel and within in I have 2 dropdownlists.   I want to show the second ddlist only when a specific value is chosen in dropdownlist1. I used Javascript/label etc on the selectedIndexChanged event but still does not work. The event gets fired and I stepped thru the code with no problems but it does not render on screen. Code snippet below. All help is wonderfully,gratefully and thankfully appreciated.

Front End

<asp:UpdatePanel ID="updPanel1" runat="server">
            <ContentTemplate>
          <asp:DropDownList ID="ddlTest1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlTest1_IndexChanged">
            <asp:ListItem Value="" Text="Select one"></asp:ListItem>
            <asp:ListItem Value="Matt" Text="Matt"></asp:ListItem>
            <asp:ListItem Value="Robin" Text="Robin"></asp:ListItem>
            </asp:DropDownList>
            <asp:DropDownList ID="ddlTest2" runat="server" style="visibility:hidden;display:none;">
            <asp:ListItem Text="Select One" Value=""></asp:ListItem>
            <asp:ListItem Text="Tom" Value="Tom"></asp:ListItem>
            <asp:ListItem Text="John" Value="John"></asp:ListItem>
            
      </asp:DropDownList>
</ContentTemplate>
            </asp:UpdatePanel>

后面的代码如下:

And the Codebehind is as follows:

Protected Sub ddlTest1_IndexChanged(ByVal sender As Object, ByVal e As EventArgs)
            If ddlTest1.SelectedValue = "Robin" Then

                  Dim script As String = "<script type=''text/javascript''>var elem=document.getElementById(''" & Me.ddlTest2.ClientID & "'');elem.style.visibility=''visible'';elem.style.display=''block'';</script>
          
Page.ClientScript.RegisterClientScriptBlock(Me.GetType(), "newKeyVal", script, True)
                  
            Else
                  Dim script As String = "<script type=''text/javascript''>var elem=document.getElementById(''" & Me.ddlTest2.ClientID & "'');elem.style.visibility=''hidden'';elem.style.display=''block'';</script>"
                  Page.ClientScript.RegisterClientScriptBlock(Me.GetType (), "newKeyVal", script, True)
                  
            End If

      End Sub

推荐答案

不要将两个下拉列表都放在Same Update Panel中.将其放在两个不同的更新面板中，并为Second Updatepanel创建UpdateMode="Conditional" ，然后从Dropdownlist1的SelectedIndexChanged事件中调用UpdatePanel2.Update().希望可以帮助您:-D

Do not put the both Dropdown list in Same Update Panel. Place it in two different Update Panel and Make the UpdateMode="Conditional" for the Second Updatepanel and call UpdatePanel2.Update() from SelectedIndexChanged event of Dropdownlist1.

Hope this will help you :-D

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