我无法在 asp.net 中获取列表框的值，在 Javascript

Question

I daynamically create options of select in javascript, and click a asp:Button to submit the added options.我每天在 javascript 中创建 select 选项，然后单击 asp:Button 以提交添加的选项。 but i can't get that from ListBox.但我无法从 ListBox 中得到它。 pls help me!!请帮助我！！

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Hello.aspx.cs" Inherits="BeyondInfo.Hello" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Welcome to My First ASP.NET</title>
    <script type="text/javascript">
        function add() {
            var count = document.getElementById("count");
            if (count.value == "") {
                count.value = 1;
            }
            count.value = parseInt(count.value) + 1;
            var num = count.value;
            var listBox2 = document.getElementById("ListBox2");
            var optn = document.createElement("OPTION");
            optn.value = num;
            optn.text = num + "_add";
            listBox2.options.add(optn);

        }

    </script>
</head>
<link href="Common.css" rel="stylesheet" />
<body>
    <form id="form1" runat="server">
        <div style="height: 277px">
            <asp:ListBox ID="ListBox2" runat="server">
                <asp:ListItem>b1222222222222222222222222222</asp:ListItem>
                <asp:ListItem>b2</asp:ListItem>
                <asp:ListItem>b3</asp:ListItem>
                <asp:ListItem>b4</asp:ListItem>
            </asp:ListBox>
            <input id="count" type="hidden" />
            <input id="btnAdd" type="button" value="ADD" onclick="add()"/>
            <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
            <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" />
    </form>
</body>
</html>
</p>

Hello.aspx.cs你好.aspx.cs

public partial class Hello : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        string sel = "";
        foreach (ListItem item in ListBox2.Items) {
            sel +=item.Text + ",";
        }
        Label1.Text = sel;
    }
}

Answer 1

Try looking at this post answer by NC01.尝试查看 NC01 的此帖子答案。 You may be able to achieve what you want by doing something similar.您可以通过做类似的事情来实现您想要的。

Basically they store the added fields in a hidden field so they are accessible server side.基本上，它们将添加的字段存储在隐藏字段中，因此它们可以在服务器端访问。

I believe that your problem is that when you add an item to a DropDownList client-side (using JavaScript) that when a PostBack occurs, the item will disappear.我相信您的问题是，当您将项目添加到 DropDownList 客户端（使用 JavaScript）时，当 PostBack 发生时，该项目将消失。 The only way around this is to add a hidden server-control to the page and when adding the item client-side, add it to the hidden server-control also, so that when a PostBack occurs you can also add it server-side.解决这个问题的唯一方法是在页面中添加一个隐藏的服务器控件，当在客户端添加项目时，也将它添加到隐藏的服务器控件中，这样当 PostBack 发生时，您也可以在服务器端添加它。

Here's an example.这是一个例子。

https://forums.asp.net/t/1287204.aspx?How+to+add+the+values+to+listbox+control+using+javascript https://forums.asp.net/t/1287204.aspx?How+to+add+the+values+to+listbox+control+using+javascript

aspx file:

<form id="Form1" method="post" runat="server">
 <asp:DropDownList id="DropDownList1" runat="server">
  <asp:listitem value="1">Item 1</asp:listitem>
  <asp:listitem value="2">Item 2</asp:listitem>
  <asp:listitem value="3">Item 3</asp:listitem>
  <asp:listitem value="4">Item 4</asp:listitem>
  <asp:listitem value="5">Item 5</asp:listitem>
  <asp:listitem value="6">Item 6</asp:listitem>
 </asp:DropDownList>
 <input id="DropDownList1NewItems" type="hidden" name="DropDownList1NewItems" runat="server">
 <input type="button" onclick="addItem();" value="Add Item">
</form>

<script type="text/javascript">
<!--
function addItem()
{
 // Add the item here...
 var ddlRef = document.getElementById('<%= DropDownList1.ClientID %>');
 var newOption = window.document.createElement('OPTION');
 newOption.text = 'SomeNewItem';
 newOption.value = 'SomeNewItem';

 ddlRef.options.add(newOption);

 var hiddenElementRef = document.getElementById('<%= DropDownList1NewItems.ClientID %>');

 if ( hiddenElementRef.value.length > 0 )
  hiddenElementRef.value += ';';

 hiddenElementRef.value += 'SomeNewItem';
}
// -->
</script>

aspx.cs file:

private void Page_Load(object sender, System.EventArgs e)
{
 if ( this.IsPostBack )
 {
  if ( DropDownList1NewItems.Value.Length > 0 )
  {
   string [] newItemsArray = DropDownList1NewItems.Value.Split(';');
   for (int i=0; i<newItemsArray.Length; i++)
   {
    string newItem = newItemsArray[i];

    DropDownList1.Items.Add(new ListItem(newItem, newItem));
   }

   DropDownList1NewItems.Value = string.Empty;
  }
 }
}

我无法在 asp.net 中获取列表框的值，在 Javascript

问题描述

1 个解决方案

解决方案1
0 2021-02-12 16:11:54

我无法在 asp.net 中获取列表框的值，在 Javascript

问题描述

1 个解决方案

解决方案1 0 2021-02-12 16:11:54

解决方案1
0 2021-02-12 16:11:54