DropDownList控件

1 <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack ="true">
2     <asp:ListItem>苹果</asp:ListItem>
3     <asp:ListItem>香蕉</asp:ListItem>
4     <asp:ListItem>橘子</asp:ListItem>
5     <asp:ListItem>桃子</asp:ListItem>
6 </asp:DropDownList>
7 <asp:Button ID="Button1" runat="server" Text="Button" OnClick ="Button1_Click"/>
8 <asp:Label ID="Label1" runat="server" Text=""></asp:Label>

 1 /// <summary>
 2 /// Button1按钮的点击事件
 3 /// </summary>
 4 /// <param name="sender"></param>
 5 /// <param name="e"></param>
 6 protected void Button1_Click(object sender, EventArgs e)
 7 {
 8     string s = string.Empty;
 9 
10     //SelectedItem：获取列表控件中索引最小的选定项。即是取的选中的值。
11     s = this.DropDownList1.SelectedItem.Text;
12 
13     this.Label1.Text = "您选中的水果是：" + s;
14 }

1  CREATE TABLE KK
2  (
3      id INT,
4      [name] VARCHAR(20),
5  )

1  INSERT INTO KK (id, [name]) VALUES (1, ‘张三‘)
2  INSERT INTO KK (id, [name]) VALUES (2, ‘李四‘)
3  INSERT INTO KK (id, [name]) VALUES (3, ‘王五‘)
4  INSERT INTO KK (id, [name]) VALUES (4, ‘赵六‘)

1 <div>
2     <asp:DropDownList ID="DropDownList1" runat="server"></asp:DropDownList>
3     <asp:Button ID="Button1" runat="server" Text="Button" OnClick ="Button1_Click"/>
4     <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
5 </div>

1   <connectionStrings>
2     <add name="connectionString" connectionString="data source = (local); database = TEMP; integrated security = true"/>
3   </connectionStrings>

 1 protected void Page_Load(object sender, EventArgs e)
 2 {
 3     if (!IsPostBack)
 4     /* 为什么判断IsPostBack:当你需要执行一些仅需要在页面第一次浏览时执行的事件
 5         * 比如页面初始化，数据绑定之类的操作时，需要将操作放在if(!IspostBack)里面，
 6         * 这样当你在点击页面中的按钮或者执行其他回发事件时，不贵再次初搜索始化或者
 7         * 重复绑定数据，提高了执行效率。
 8         */
 9     {
10         string connectionString = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
11 
12         SqlConnection connection = new SqlConnection(connectionString);
13 
14         connection.Open();
15 
16         string sql = "SELECT * FROM KK";
17 
18         SqlCommand cmd = new SqlCommand(sql, connection);
19 
20         SqlDataReader sdr = cmd.ExecuteReader();
21 
22         //任意给的字段名，只要是想显示在界面上的就行。其值给了：Text
23         this.DropDownList1.DataTextField = "name";
24 
25         //任意给得字段名，只要是想在后台看到前台看不到的数据就行。其值给了：Value
26         this.DropDownList1.DataValueField = "id";//此字段可以去掉。value的值默认为Text的值。
27 
28         this.DropDownList1.DataSource = sdr;
29 
30         this.DropDownList1.DataBind();
31 
32         sdr.Close();
33 
34         connection.Close();
35     }
36 }

 1 /// <summary>
 2 /// Button1按钮的点击事件
 3 /// </summary>
 4 /// <param name="sender"></param>
 5 /// <param name="e"></param>
 6 protected void Button1_Click(object sender, EventArgs e)
 7 {
 8     string s = string.Empty;
 9 
10     //SelectedItem：获取列表控件中索引最小的选定项。即是取的选中的值。
11     s = this.DropDownList1.SelectedItem.Text;
12 
13     this.Label1.Text = "您选中的是：" + s;
14 }