DropDownList control in asp.net

DropDownList control is similar to a RadioButtonList control with less screen read state. We can add options to a DropDownList in many ways: we can add items directly to the ListItemCollection collection of the DropDownList control, we can bind a DropDownList control to a dataSource, or we can also bind a DropDownList control at the time of declaration.

If you want to add items at the time of declaration:

    <asp:DropDownList ID="DropDownList1" runat="server">
      <asp:ListItem Text="USA"/>
      <asp:ListItem Text="India"/>
      <asp:ListItem Text="Japan"/>
    </asp:DropDownList>

And if you want to add List items directly to the ListItemCollection collection of the DropDownList control, for example:

<%@ Page Language="VB" AutoEventWireup="true" CodeFile="Default.aspx.vb" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    Sub Page_Load()
        If Not IsPostBack Then
            DropDownList1.Items.Add("USA")
            DropDownList1.Items.Add("India")
            DropDownList1.Items.Add("Japan")
        End If
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>bind DropDownList control</title>
</head>
<body style="height: 410px; width: 768px">
    <form runat="server">
    <asp:DropDownList ID="DropDownList1" runat="server">
    </asp:DropDownList>
    </form>
</body>
</html>

And in the last if you want to bind control to a DataSource, for example:
In the following example first we create a arraylist and then we assign this arraylist to datasource property of DropDownList control

<%@ Page Language="VB" AutoEventWireup="true" CodeFile="Default.aspx.vb" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    Sub Page_Load()
        Dim arrList As New ArrayList
        arrList.Add("USA")
        arrList.Add("India")
        arrList.Add("Japan")
        DropDownList1.DataSource = arrList
        DropDownList1.DataBind()
    End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>bind DropDownList control</title>
</head>
<body style="height: 410px; width: 768px">
    <form runat="server">
    <asp:DropDownList ID="DropDownList1" runat="server">
    </asp:DropDownList>
    </form>
</body>
</html>