ASP.NET Tutorial/ASP.net Controls/DropDownList

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Dynamically generating a DropDownList control from an array (C#)

<%@ Page Language="C#" %>
<script runat="server">
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        string[] CarArray = new string[4] {"Ford", "Honda", "BMW", "Dodge"};
        string[] AirplaneArray = new string[3] {"Boeing 777", "Boeing 747","Boeing 737"};
        string[] TrainArray = new string[3] {"Bullet Train", "Amtrack", "Tram"};
        
        if (DropDownList1.SelectedValue == "Car") {
            DropDownList2.DataSource = CarArray; }
        else if (DropDownList1.SelectedValue == "Airplane") {
            DropDownList2.DataSource = AirplaneArray; }
        else {
            DropDownList2.DataSource = TrainArray; 
        }
                
        DropDownList2.DataBind();
        DropDownList2.Visible = true;
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        Response.Write("You selected <b>" +
           DropDownList1.SelectedValue.ToString() + ": " +
           DropDownList2.SelectedValue.ToString() + "</b>");
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>DropDownList Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        Select transportation type:<br />
        <asp:DropDownList ID="DropDownList1" 
                          Runat="server" 
                          OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" 
                          AutoPostBack="true">
            <asp:ListItem>Select an Item</asp:ListItem>
            <asp:ListItem>Car</asp:ListItem>
            <asp:ListItem>Airplane</asp:ListItem>
            <asp:ListItem>Train</asp:ListItem>
        </asp:DropDownList>&nbsp;
        <asp:DropDownList ID="DropDownList2" Runat="server" Visible="false">
        </asp:DropDownList>
        <asp:Button ID="Button1" Runat="server" Text="Select Options" 
         OnClick="Button1_Click" />
    </div>
    </form>
</body>
</html>


Dynamically generating a DropDownList control from an array (VB)

<%@ Page Language="VB" %>
<script runat="server">
    Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, _
      ByVal e As System.EventArgs)
        Dim CarArray() As String = {"Ford", "Honda", "BMW", "Dodge"}
        Dim AirplaneArray() As String = {"Boeing 777", "Boeing 747", "Boeing 737"}
        Dim TrainArray() As String = {"Bullet Train", "Amtrack", "Tram"}
        
        If DropDownList1.SelectedValue = "Car" Then
            DropDownList2.DataSource = CarArray
        ElseIf DropDownList1.SelectedValue = "Airplane" Then
            DropDownList2.DataSource = AirplaneArray
        Else
            DropDownList2.DataSource = TrainArray
        End If
        
        DropDownList2.DataBind()
        DropDownList2.Visible = True
    End Sub
    Protected Sub Button1_Click(ByVal sender As Object, _
       ByVal e As System.EventArgs)
        Response.Write("You selected <b>" & _
           DropDownList1.SelectedValue.ToString() & ": " & _
           DropDownList2.SelectedValue.ToString() & "</b>")
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>DropDownList Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        Select transportation type:<br />
        <asp:DropDownList ID="DropDownList1" Runat="server" 
         OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" 
         AutoPostBack="true">
            <asp:ListItem>Select an Item</asp:ListItem>
            <asp:ListItem>Car</asp:ListItem>
            <asp:ListItem>Airplane</asp:ListItem>
            <asp:ListItem>Train</asp:ListItem>
        </asp:DropDownList>&nbsp;
        <asp:DropDownList ID="DropDownList2" Runat="server" Visible="false">
        </asp:DropDownList>
        <asp:Button ID="Button1" Runat="server" Text="Select Options" 
         OnClick="Button1_Click" />
    </div>
    </form>
</body>
</html>


Get selected index from asp:dropdownlist

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="MyPage" %>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Label ID="Label1" runat="server" Style="z-index: 100; left: 151px; position: absolute;
            top: 120px" Text="What is the date"></asp:Label>
        <asp:Label ID="result" runat="server" Height="25px" Style="z-index: 101; left: 159px;
            position: absolute; top: 242px" Text="Label" Width="324px"></asp:Label>
        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" Height="48px"
            Style="z-index: 102; left: 274px; position: absolute; top: 118px" Width="243px">
        </asp:DropDownList>
        <asp:Button ID="Button1" runat="server" Style="z-index: 104; left: 393px; position: absolute;
            top: 168px" Text="OK" />
    
    </div>
    </form>
</body>
</html>

File: Default.aspx.vb

Partial Class MyPage
    Inherits System.Web.UI.Page
    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Select Case Me.DropDownList1.SelectedIndex
            Case 0
                Me.result.Text = "A"
            Case 1
                Me.result.Text = "B"
            Case 2
                Me.result.Text = "C"
            Case 3
                Me.result.Text = "D"
            Case 4
                Me.result.Text = "E"
            Case 5
                Me.result.Text = "F"
            Case 6
                Me.result.Text = "G"
            Case 7
                Me.result.Text = "H"
            Case 8
                Me.result.Text = "I"
            Case 9
                Me.result.Text = "J"
            Case 10
                Me.result.Text = "K"
            Case 11
                Me.result.Text = "L"
        End Select
    End Sub
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Page.IsPostBack = False Then
            Me.DropDownList1.Items.Add("A")
            Me.DropDownList1.Items.Add("B")
            Me.DropDownList1.Items.Add("C")
            Me.DropDownList1.Items.Add("D")
            Me.DropDownList1.Items.Add("E")
            Me.DropDownList1.Items.Add("F")
            Me.DropDownList1.Items.Add("G")
            Me.DropDownList1.Items.Add("H")
            Me.DropDownList1.Items.Add("I")
            Me.DropDownList1.Items.Add("J")
            Me.DropDownList1.Items.Add("K")
            Me.DropDownList1.Items.Add("L")
        End If
    End Sub
End Class


Get selected item in DropDownList

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="DropDownList" %>
<!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>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        What is your favorite ice cream flavor? 
        <asp:DropDownList ID="flavors" runat="server">
            <asp:ListItem>A</asp:ListItem>
            <asp:ListItem>B</asp:ListItem>
            <asp:ListItem>C</asp:ListItem>
        </asp:DropDownList>
        <br /> 
        <asp:Button ID="btnSubmit" runat="server" Text="Click Me" />
        <br />
        <br />
        <asp:Label ID="results" runat="server"></asp:Label></div>
    </form>
</body>
</html>

File: Default.aspx.vb

Partial Class DropDownList
    Inherits System.Web.UI.Page
    Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
        results.Text = "You like " & flavors.SelectedItem.Text
    End Sub
End Class
Источник — «http://nfex.ru/index.php?title=ASP.NET_Tutorial/ASP.net_Controls/DropDownList&oldid=3397»