DropDownList Web Server Control Declarative Syntax
[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]
Enables users to select from a single selection drop-down list. The drop-down list can contain any number of items.
<asp:DropDownList
AccessKey="string"
AppendDataBoundItems="True|False"
AutoPostBack="True|False"
BackColor="color name|#dddddd"
BorderColor="color name|#dddddd"
BorderStyle="NotSet|None|Dotted|Dashed|Solid|Double|Groove|Ridge|
Inset|Outset"
BorderWidth="size"
CausesValidation="True|False"
CssClass="string"
DataMember="string"
DataSource="string"
DataSourceID="string"
DataTextField="string"
DataTextFormatString="string"
DataValueField="string"
Enabled="True|False"
EnableTheming="True|False"
EnableViewState="True|False"
Font-Bold="True|False"
Font-Italic="True|False"
Font-Names="string"
Font-Overline="True|False"
Font-Size="string|Smaller|Larger|XX-Small|X-Small|Small|Medium|
Large|X-Large|XX-Large"
Font-Strikeout="True|False"
Font-Underline="True|False"
ForeColor="color name|#dddddd"
Height="size"
ID="string"
OnDataBinding="DataBinding event handler"
OnDataBound="DataBound event handler"
OnDisposed="Disposed event handler"
OnInit="Init event handler"
OnLoad="Load event handler"
OnPreRender="PreRender event handler"
OnSelectedIndexChanged="SelectedIndexChanged event handler"
OnTextChanged="TextChanged event handler"
OnUnload="Unload event handler"
runat="server"
SelectedIndex="integer"
SelectedValue="string"
SkinID="string"
Style="string"
TabIndex="integer"
ToolTip="string"
ValidationGroup="string"
Visible="True|False"
Width="size"
>
<asp:ListItem
Enabled="True|False"
Selected="True|False"
Text="string"
Value="string"
/>
</asp:DropDownList>
Remarks
Use the DropDownList control to create a single selection drop-down list control. You can control the appearance of the DropDownList control by setting the BorderColor, BorderStyle, and BorderWidth properties.
To specify the items that appear in the DropDownList control, place a ListItem element for each entry between the opening and closing tags of the DropDownList control.
The DropDownList control also supports data binding. To bind the control to a data source, first create a data source, such as a ArrayList, that contains the items to display in the control. Next, use the DataBind method to bind the data source to the DropDownList control. Use the DataTextField and DataValueField properties to specify which field in the data source to bind to the Text and Value properties of each list item in the control, respectively. The DropDownList control will now display the information from the data source.
Use the SelectedIndex property to programmatically determine the index of the item selected by the user from the DropDownList control. The index can then be used to retrieve the selected item from the Items collection of the control.
For detailed information on the DropDownList Web server control's properties and events, see the DropDownList documentation.
Example
The following code example demonstrates how to create a DropDownList control that contains four items.
<%@ Page Language="VB" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" >
<script runat="server" >
Sub Selection_Change(sender As Object, e As EventArgs)
' Set the background color for days in the Calendar control
' based on the value selected by the user from the
' DropDownList control.
Calendar1.DayStyle.BackColor = _
System.Drawing.Color.FromName(ColorList.SelectedItem.Value)
End Sub
</script>
<head runat="server">
<title> DropDownList Example </title>
</head>
<body>
<form id="form1" runat="server">
<h3> DropDownList Example </h3>
Select a background color for days in the calendar.
<br /><br />
<asp:Calendar id="Calendar1"
ShowGridLines="True"
ShowTitle="True"
runat="server"/>
<br /><br />
<table cellpadding="5">
<tr>
<td>
Background color:
</td>
</tr>
<tr>
<td>
<asp:DropDownList id="ColorList"
AutoPostBack="True"
OnSelectedIndexChanged="Selection_Change"
runat="server">
<asp:ListItem Selected="True" Value="White"> White </asp:ListItem>
<asp:ListItem Value="Silver"> Silver </asp:ListItem>
<asp:ListItem Value="DarkGray"> Dark Gray </asp:ListItem>
<asp:ListItem Value="Khaki"> Khaki </asp:ListItem>
<asp:ListItem Value="DarkKhaki"> Dark Khaki </asp:ListItem>
</asp:DropDownList>
</td>
</tr>
</table>
</form>
</body>
</html>
<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" >
<script runat="server" >
void Selection_Change(Object sender, EventArgs e)
{
// Set the background color for days in the Calendar control
// based on the value selected by the user from the
// DropDownList control.
Calendar1.DayStyle.BackColor =
System.Drawing.Color.FromName(ColorList.SelectedItem.Value);
}
</script>
<head runat="server">
<title> DropDownList Example </title>
</head>
<body>
<form id="form1" runat="server">
<h3> DropDownList Example </h3>
Select a background color for days in the calendar.
<br /><br />
<asp:Calendar id="Calendar1"
ShowGridLines="True"
ShowTitle="True"
runat="server"/>
<br /><br />
<table cellpadding="5">
<tr>
<td>
Background color:
</td>
</tr>
<tr>
<td>
<asp:DropDownList id="ColorList"
AutoPostBack="True"
OnSelectedIndexChanged="Selection_Change"
runat="server">
<asp:ListItem Selected="True" Value="White"> White </asp:ListItem>
<asp:ListItem Value="Silver"> Silver </asp:ListItem>
<asp:ListItem Value="DarkGray"> Dark Gray </asp:ListItem>
<asp:ListItem Value="Khaki"> Khaki </asp:ListItem>
<asp:ListItem Value="DarkKhaki"> Dark Khaki </asp:ListItem>
</asp:DropDownList>
</td>
</tr>
</table>
</form>
</body>
</html>
The following code example demonstrates how to populate a DropDownList control through declarative data binding.
<%@ Page Language="VB"%>
<%@ Import Namespace="System.Drawing" %>
<!DOCTYPE html PUBLIC
"-//W3C//DTD XHTML 1.0 Transitional//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" >
<head runat="server">
<title>DropDownList Declarative DataBinding Sample</title>
<script runat="server">
Sub Selection_Change(ByVal sender As Object, ByVal e As EventArgs)
'' Set the background color for days in the Calendar control
'' based on the value selected by the user from the
'' DropDownList control.
Calendar1.DayStyle.BackColor = _
Color.FromName(ColorList.SelectedItem.Value)
End Sub
</script>
</head>
<body>
<form id="form1" runat="server">
<asp:XmlDataSource ID="Colors" runat="server">
<Data>
<Colors>
<Color ColorID="White" ColorName="White" />
<Color ColorID="Silver" ColorName="Silver" />
<Color ColorID="DarkGray" ColorName="Dark Gray" />
<Color ColorID="Khaki" ColorName="Khaki" />
<Color ColorID="DarkKhaki" ColorName="Dark Khaki" />
</Colors>
</Data>
</asp:XmlDataSource>
Colors: <asp:DropDownList ID="ColorList"
DataSourceID="Colors"
DataTextField="ColorName"
DataValueField="ColorID"
runat="server"
AutoPostBack="true"
OnSelectedIndexChanged="Selection_Change" />
<p />
<asp:Calendar ID="Calendar1" runat="server" />
</form>
</body>
</html>
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Drawing" %>
<!DOCTYPE html PUBLIC
"-//W3C//DTD XHTML 1.0 Transitional//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" >
<head runat="server">
<title>DropDownList Declarative DataBinding Sample</title>
<script runat="server">
void Selection_Change(Object sender, EventArgs e)
{
// Set the background color for days in the Calendar control
// based on the value selected by the user from the
// DropDownList control.
Calendar1.DayStyle.BackColor =
Color.FromName(ColorList.SelectedItem.Value);
}
</script>
</head>
<body>
<form id="form1" runat="server">
<asp:XmlDataSource ID="Colors" runat="server">
<Data>
<Colors>
<Color ColorID="White" ColorName="White" />
<Color ColorID="Silver" ColorName="Silver" />
<Color ColorID="DarkGray" ColorName="Dark Gray" />
<Color ColorID="Khaki" ColorName="Khaki" />
<Color ColorID="DarkKhaki" ColorName="Dark Khaki" />
</Colors>
</Data>
</asp:XmlDataSource>
Colors: <asp:DropDownList ID="ColorList"
DataSourceID="Colors"
DataTextField="ColorName"
DataValueField="ColorID"
runat="server"
AutoPostBack="true"
OnSelectedIndexChanged="Selection_Change" />
<p />
<asp:Calendar ID="Calendar1" runat="server" />
</form>
</body>
</html>
The following code example demonstrates how to create a DropDownList control though programmatic data binding.
<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" >
<script runat="server" >
Sub Selection_Change(sender as Object, e As EventArgs)
' Set the background color for days in the Calendar control
' based on the value selected by the user from the
' DropDownList control.
Calendar1.DayStyle.BackColor = _
System.Drawing.Color.FromName(ColorList.SelectedItem.Value)
End Sub
Sub Page_Load(sender as Object, e As EventArgs)
' Load data for the DropDownList control only once, when the
' page is first loaded.
If Not IsPostBack Then
' Specify the data source and field names for the Text
' and Value properties of the items (ListItem objects)
' in the DropDownList control.
ColorList.DataSource = CreateDataSource()
ColorList.DataTextField = "ColorTextField"
ColorList.DataValueField = "ColorValueField"
' Bind the data to the control.
ColorList.DataBind()
' Set the default selected item, if desired.
ColorList.SelectedIndex = 0
End If
End Sub
Function CreateDataSource() As ICollection
' Create a table to store data for the DropDownList control.
Dim dt As DataTable = New DataTable()
' Define the columns of the table.
dt.Columns.Add(new DataColumn("ColorTextField", GetType(String)))
dt.Columns.Add(new DataColumn("ColorValueField", GetType(String)))
' Populate the table with sample values.
dt.Rows.Add(CreateRow("White", "White", dt))
dt.Rows.Add(CreateRow("Silver", "Silver", dt))
dt.Rows.Add(CreateRow("Dark Gray", "DarkGray", dt))
dt.Rows.Add(CreateRow("Khaki", "Khaki", dt))
dt.Rows.Add(CreateRow("Dark Khaki", "DarkKhaki", dt))
' Create a DataView from the DataTable to act as the data source
' for the DropDownList control.
Dim dv As DataView = New DataView(dt)
Return dv
End Function
Function CreateRow(Text As String, Value As String, dt As DataTable) As DataRow
' Create a DataRow using the DataTable defined in the
' CreateDataSource method.
Dim dr As DataRow = dt.NewRow()
' This DataRow contains the ColorTextField and ColorValueField
' fields, as defined in the CreateDataSource method. Set the
' fields with the appropriate value. Remember that column 0
' is defined as ColorTextField, and column 1 is defined as
' ColorValueField.
dr(0) = Text
dr(1) = Value
Return dr
End Function
</script>
<head runat="server">
<title> DropDownList Data Binding Example </title>
</head>
<body>
<form id="form1" runat="server">
<h3> DropDownList Data Binding Example </h3>
Select a background color for days in the calendar.
<br /><br />
<asp:Calendar id="Calendar1"
ShowGridLines="True"
ShowTitle="True"
runat="server"/>
<br /><br />
<table cellpadding="5">
<tr>
<td>
Background color:
</td>
</tr>
<tr>
<td>
<asp:DropDownList id="ColorList"
AutoPostBack="True"
OnSelectedIndexChanged="Selection_Change"
runat="server"/>
</td>
</tr>
</table>
</form>
</body>
</html>
<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" >
<script runat="server" >
void Selection_Change(Object sender, EventArgs e)
{
// Set the background color for days in the Calendar control
// based on the value selected by the user from the
// DropDownList control.
Calendar1.DayStyle.BackColor =
System.Drawing.Color.FromName(ColorList.SelectedItem.Value);
}
void Page_Load(Object sender, EventArgs e)
{
// Load data for the DropDownList control only once, when the
// page is first loaded.
if(!IsPostBack)
{
// Specify the data source and field names for the Text
// and Value properties of the items (ListItem objects)
// in the DropDownList control.
ColorList.DataSource = CreateDataSource();
ColorList.DataTextField = "ColorTextField";
ColorList.DataValueField = "ColorValueField";
// Bind the data to the control.
ColorList.DataBind();
// Set the default selected item, if desired.
ColorList.SelectedIndex = 0;
}
}
ICollection CreateDataSource()
{
// Create a table to store data for the DropDownList control.
DataTable dt = new DataTable();
// Define the columns of the table.
dt.Columns.Add(new DataColumn("ColorTextField", typeof(String)));
dt.Columns.Add(new DataColumn("ColorValueField", typeof(String)));
// Populate the table with sample values.
dt.Rows.Add(CreateRow("White", "White", dt));
dt.Rows.Add(CreateRow("Silver", "Silver", dt));
dt.Rows.Add(CreateRow("Dark Gray", "DarkGray", dt));
dt.Rows.Add(CreateRow("Khaki", "Khaki", dt));
dt.Rows.Add(CreateRow("Dark Khaki", "DarkKhaki", dt));
// Create a DataView from the DataTable to act as the data source
// for the DropDownList control.
DataView dv = new DataView(dt);
return dv;
}
DataRow CreateRow(String Text, String Value, DataTable dt)
{
// Create a DataRow using the DataTable defined in the
// CreateDataSource method.
DataRow dr = dt.NewRow();
// This DataRow contains the ColorTextField and ColorValueField
// fields, as defined in the CreateDataSource method. Set the
// fields with the appropriate value. Remember that column 0
// is defined as ColorTextField, and column 1 is defined as
// ColorValueField.
dr[0] = Text;
dr[1] = Value;
return dr;
}
</script>
<head runat="server">
<title> DropDownList Data Binding Example </title>
</head>
<body>
<form id="form1" runat="server">
<h3> DropDownList Data Binding Example </h3>
Select a background color for days in the calendar.
<br /><br />
<asp:Calendar id="Calendar1"
ShowGridLines="True"
ShowTitle="True"
runat="server"/>
<br /><br />
<table cellpadding="5">
<tr>
<td>
Background color:
</td>
</tr>
<tr>
<td>
<asp:DropDownList id="ColorList"
AutoPostBack="True"
OnSelectedIndexChanged="Selection_Change"
runat="server"/>
</td>
</tr>
</table>
</form>
</body>
</html>
See Also
Reference
DropDownList Web Server Control Overview