用Javascript为DropDownList控件下拉式选择添加一个Item至定义索引位置。
准备数据，创建一个对象，将是存储DropDownList控件每个Item数据。
Imports Microsoft.VisualBasicNamespace Insus.NET Public Class Catalog Private _ID As Integer Private _Name As String Public Property ID As Integer Get Return _ID End Get Set(value As Integer) _ID = value End Set End Property Public Property Name As String Get Return _Name End Get Set(value As String) _Name = value End Set End Property End ClassEnd Namespace
在.aspx放置一个DropDownList控件：
<asp:DropDownList ID="DropDownListCatalog" runat="server"></asp:DropDownList>
在.aspx.vb绑定数据：
Imports Insus.NETPartial Class _Default Inherits System.Web.UI.Page Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load If Not IsPostBack Then Data_Binding() End If End Sub Private Sub Data_Binding() Me.DropDownListCatalog.DataSource = GetData() Me.DropDownListCatalog.DataValueField = "ID" Me.DropDownListCatalog.DataTextField = "Name" Me.DropDownListCatalog.DataBind() End Sub Private Function GetData() As List(Of Catalog) Dim cls As New List(Of Catalog) Dim cl As Catalog = New Catalog() cl.ID = 1 cl.Name = "新闻频道" cls.Add(cl) cl = New Catalog() cl.ID = 2 cl.Name = "体育频道" cls.Add(cl) cl = New Catalog() cl.ID = 3 cl.Name = "军事频道" cls.Add(cl) cl = New Catalog() cl.ID = 4 cl.Name = "教育频道" cls.Add(cl) Return cls End FunctionEnd Class
准备数据与环境后，写Javascript:
window.onload = function () { var catalog = document.getElementById("<%=DropDownListCatalog.ClientID%>"); var obj = document.createElement("option") obj.text = "请选择..." obj.value = 0 catalog.options.insertBefore(obj, catalog.options[0]); }
DEMO: