动态为DropDownList添加Item-原创手记-慕课网

Insus.NET在MasterPage放置了一个DropDownList和一个Button控件，然后在Default.aspx放置一个TextBox。从上面的动画中可以看到，在TextBox输入文字，它会动态添加至MasterPage的DropDownList控件中。

实现过程，首先写一个接口：

IGetable using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

/// <summary>
/// Summary description for IGetable
/// </summary>
namespace Insus.NET
{
    public interface IGetable
    {
        string TextBoxValue
        {
            get;
        }
    }
}

接下来，新建MasterPage：

InsusMasterPage.master:

InsusMasterPage.master <%@ Master Language="C#" AutoEventWireup="true" CodeFile="InsusMasterPage.master.cs" Inherits="InsusMasterPage" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="DropDownList1" runat="server" Width="100">
        </asp:DropDownList>
        <asp:Button ID="Button1" runat="server" Text="Add Item" OnClick="Button1_Click" />
        <asp:ContentPlaceHolder id="ContentPlaceHolder1" runat="server">

        </asp:ContentPlaceHolder>
    </div>
    </form>
</body>
</html>

InsusMasterPage.master.cs代码，重点部分已经有注释，难度应该不大:

InsusMasterPage.master.cs using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Insus.NET;

public partial class InsusMasterPage : System.Web.UI.MasterPage
{
   //Insus.NET:宣告一个泛型，将存储输入的数据
    List<string> list = new List<string>();

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            Data_Binding();
        }
    }

    private void Data_Binding()
    {
        this.DropDownList1.DataSource = list;
        this.DropDownList1.DataBind();

    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        //Insus.NET:把page转为接口，并取属性
        string v = ((IGetable)this.Page).TextBoxValue;

       //Insus.NET:判断Session是否为空
        if (Session["db"] != null)
        {
           //Insus.NET:如果不为空，直接从Session取出
            list = (List<string>)Session["db"];
        }
        else
        {
            //Insus.NET:如果为空，new一个实例
            list = new List<string>();
        }

       //Insus.NET:把输入值加入泛型
        list.Add(v);

        //Insus.NET:存入Session
        Session["db"] = list;

        Data_Binding();
    }
}

最后，是Aspx的代码：

Default.aspx:

View Code <%@ Page Title="" Language="C#" MasterPageFile="~/InsusMasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</asp:Content>

Default.aspx.cs:

View Code using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Insus.NET;

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

    }

    //Insus.NET：实现接口
    public string TextBoxValue
    {
        get {
            return this.TextBox1.Text;
        }
    }
}

好了，非常简单的例子。