从一个列表到另一个列表的Javascript

我有一个从db填写的列表是userlist，如下所示：

<select id="Userlist" name="cars" runat="server" multiple="true" style="width: 270px; height: 200px;">
</select>

另一个我试过的是

           var user = document.getElementById("Userlist");
            var seluser = user.selectedIndex;

            if (seluser == -1) {
                window.alert("You must first select an item on the left side.")
            }
            else {
                var toChoose = document.getElementById("ToChoose");
                var newOption = user[seluser].cloneNode(true);
                toChoose.appendChild(newOption);
            }

编辑：这是我从数据库中填写用户列表的方式

        string mycommand = "SELECT [id], [username] FROM [users]";
        SqlDataAdapter x = new SqlDataAdapter(mycommand, ConnectionString);
        DataSet ds = new DataSet();
        x.Fill(ds, "users");
        DataTable dt = ds.Tables[0];
        Userlist.DataSource = dt;
        Userlist.DataTextField = "username";
        Userlist.DataValueField = "username";
        Userlist.DataBind();

---

我想，也许你用错了Userlist的Id。如果您将所有代码发布到视图中，每个人都可以更好地帮助您

这是一个样本。希望能帮上忙，我的朋友：））

1） 在代码隐藏中创建示例数据

public partial class About : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

            DataTable dtName = new DataTable();

            //Add Columns to Table
            dtName.Columns.Add(new DataColumn("DisplayMember"));
            dtName.Columns.Add(new DataColumn("ValueMember"));

            //Now Add Values
            dtName.Rows.Add("Suits", "0");
            dtName.Rows.Add("Harvey Spector", "1");
            dtName.Rows.Add("Jessica Pearson", "2");
            dtName.Rows.Add("Mike Ross", "3");
            dtName.Rows.Add("Donna Paulson", "4");
            dtName.Rows.Add("Rachel", "5");

            //Bind data to Userlist     
            Userlist.DataSource = dtName;
            Userlist.DataTextField = dtName.Columns["DisplayMember"].ToString();
            Userlist.DataValueField = dtName.Columns["ValueMember"].ToString();
            Userlist.DataBind();
        }
    }

2） 看法

.
您的应用程序描述页面。
使用此区域可提供其他信息

函数validateUser（）{
var selItem=document.getElementById（“MainContent\u Userlist”）。选择索引；
如果（selItem==-1）{
window.alert（“您必须首先选择左侧的项目。”）
}否则{
document.getElementById（“ToChoose”）.add（document.getElementById（“MainContent\u Userlist”）[selItem]，null）；
}
}

问题是？。说得好，对不起，我忘了提这个了。问题是为什么我不能从Userlist中将此选定项插入到Choose？当我在网上尝试时，这些功能正在运行。你可以在这里查看：非常感谢。我唯一缺少的是将主要内容添加到用户列表之前。你救了我的命。祝你一切顺利：）

        string mycommand = "SELECT [id], [username] FROM [users]";
        SqlDataAdapter x = new SqlDataAdapter(mycommand, ConnectionString);
        DataSet ds = new DataSet();
        x.Fill(ds, "users");
        DataTable dt = ds.Tables[0];
        Userlist.DataSource = dt;
        Userlist.DataTextField = "username";
        Userlist.DataValueField = "username";
        Userlist.DataBind();

public partial class About : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

            DataTable dtName = new DataTable();

            //Add Columns to Table
            dtName.Columns.Add(new DataColumn("DisplayMember"));
            dtName.Columns.Add(new DataColumn("ValueMember"));

            //Now Add Values
            dtName.Rows.Add("Suits", "0");
            dtName.Rows.Add("Harvey Spector", "1");
            dtName.Rows.Add("Jessica Pearson", "2");
            dtName.Rows.Add("Mike Ross", "3");
            dtName.Rows.Add("Donna Paulson", "4");
            dtName.Rows.Add("Rachel", "5");

            //Bind data to Userlist     
            Userlist.DataSource = dtName;
            Userlist.DataTextField = dtName.Columns["DisplayMember"].ToString();
            Userlist.DataValueField = dtName.Columns["ValueMember"].ToString();
            Userlist.DataBind();
        }
    }

<%@ Page Title="About" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="About.aspx.cs" Inherits="WebFormSample.About" %>

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">
    <h2><%: Title %>.</h2>
    <h3>Your application description page.</h3>
    <p>Use this area to provide additional information.</p>

    <select id="Userlist" name="cars" runat="server" multiple="true" style="width: 270px; height: 200px;">
    </select>

    <select id="ToChoose" name="cars" multiple="multiple" style="width: 270px; height: 200px;"></select>

    <input id="ButtonAddUsers" onclick="return validateUser();" type="button" value="Add" />


    <script>
        function validateUser() {
            var selItem = document.getElementById("MainContent_Userlist").selectedIndex;
            if (selItem == -1) {
                window.alert("You must first select an item on the left side.")
            } else {
                document.getElementById("ToChoose").add(document.getElementById("MainContent_Userlist")[selItem], null);
            }
        }
    </script>
</asp:Content>