DataList.OnItemCommand Method (System.Web.UI.WebControls)

OnItemCommand Method

.NET Framework Class Library

DataList..::.OnItemCommand Method

Raises the ItemCommand event. This allows you to provide a custom handler for the event.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in System.Web.dll)

Syntax

Visual Basic (Declaration)

Protected Overridable Sub OnItemCommand ( _
    e As DataListCommandEventArgs _
)

Visual Basic (Usage)

Dim e As DataListCommandEventArgs

Me.OnItemCommand(e)

protected virtual void OnItemCommand(
    DataListCommandEventArgs e
)

Visual C++

protected:
virtual void OnItemCommand(
    DataListCommandEventArgs^ e
)

JScript

protected function OnItemCommand(
    e : DataListCommandEventArgs
)

Parameters

e: Type: System.Web.UI.WebControls..::.DataListCommandEventArgs
A DataListCommandEventArgs that contains event data.

Remarks

Use the OnItemCommand method to provide a custom handler for the ItemCommand event.

The ItemCommand event is raised when any button is clicked in the DataList control and is commonly used when you have a button control with a custom CommandName value, such as Add, in the DataList control.

Raising an event invokes the event handler through a delegate. For more information, see How to: Consume Events in a Web Forms Application.

The OnItemCommand method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors:

When overriding OnItemCommand in a derived class, be sure to call the base class's OnItemCommand method so that registered delegates receive the event.

Examples

The following code example demonstrates how to specify and code a handler for the ItemCommand event to select an item from the DataList control.

Note:
The following code sample uses the single-file code model and may not work correctly if copied directly into a code-behind file. This code sample must be copied into an empty text file that has an .aspx extension. For more information on the Web Forms code model, see ASP.NET Web Page Code Model.

Visual Basic

<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head>
    <title>DataList Select Example</title>
<script runat="server">

      Function CreateDataSource() As ICollection 

         ' Create sample data for the DataList control.
         Dim dt As DataTable = New DataTable()
         Dim dr As DataRow

         ' Define the columns of the table.
         dt.Columns.Add(New DataColumn("Item", GetType(Int32)))
         dt.Columns.Add(New DataColumn("Qty", GetType(Int32)))
         dt.Columns.Add(New DataColumn("Price", GetType(Double)))

         ' Populate the table with sample values.
         Dim i As Integer

         For i = 0 To 8 

            dr = dt.NewRow()

            dr(0) = i
            dr(1) = i * 2
            dr(2) = 1.23 * (i + 1)

            dt.Rows.Add(dr)

         Next i

         Dim dv As DataView = New DataView(dt)
         Return dv

      End Function

      Sub Page_Load(sender As Object, e As EventArgs) 

         ' Load sample data only once, when the page is first loaded.
         If Not IsPostBack Then 

            ItemsList.DataSource = CreateDataSource()
            ItemsList.DataBind()

         End If

      End Sub

      Sub Item_Command(sender As Object, e As DataListCommandEventArgs) 

         ' Set the SelectedIndex property to select an item in the DataList.
         ItemsList.SelectedIndex = e.Item.ItemIndex

         ' Rebind the data source to the DataList to refresh the control.
         ItemsList.DataSource = CreateDataSource()
         ItemsList.DataBind()

      End Sub

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>DataList Select Example</h3>

      Click <b>Select</b> to select an item.

      <br /><br />

      <asp:DataList id="ItemsList"
           GridLines="Both"
           CellPadding="3"
           CellSpacing="0"           
           OnItemCommand="Item_Command"
           runat="server">

         <HeaderStyle BackColor="#aaaadd">
         </HeaderStyle>

         <AlternatingItemStyle BackColor="Gainsboro">
         </AlternatingItemStyle>

         <SelectedItemStyle BackColor="Yellow">
         </SelectedItemStyle>

         <HeaderTemplate>

            Items

         </HeaderTemplate>

         <ItemTemplate>

            <asp:LinkButton id="SelectButton" 
                 Text="Select" 
                 CommandName="Select"
                 runat="server"/>

            Item <%# DataBinder.Eval(Container.DataItem, "Item") %>

         </ItemTemplate>

         <SelectedItemTemplate>

            Item:
            <asp:Label id="ItemLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Item") %>' 
                 runat="server"/>

            <br />

            Quantity:
            <asp:Label id="QtyLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Qty") %>' 
                 runat="server"/>

            <br />

            Price:
            <asp:Label id="PriceLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>' 
                 runat="server"/>

         </SelectedItemTemplate>

      </asp:DataList>

   </form>

</body>
</html>

<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head>
    <title>DataList Select Example</title>
<script runat="server">

      ICollection CreateDataSource() 
      {

         // Create sample data for the DataList control.
         DataTable dt = new DataTable();
         DataRow dr;

         // Define the columns of the table.
         dt.Columns.Add(new DataColumn("Item", typeof(Int32)));
         dt.Columns.Add(new DataColumn("Qty", typeof(Int32)));
         dt.Columns.Add(new DataColumn("Price", typeof(double)));

         // Populate the table with sample values.
         for (int i = 0; i < 9; i++) 
         {
            dr = dt.NewRow();

            dr[0] = i;
            dr[1] = i * 2;
            dr[2] = 1.23 * (i + 1);

            dt.Rows.Add(dr);
         }

         DataView dv = new DataView(dt);
         return dv;

      }

      void Page_Load(Object sender, EventArgs e) 
      {

         // Load sample data only once, when the page is first loaded.
         if (!IsPostBack) 
         {
            ItemsList.DataSource = CreateDataSource();
            ItemsList.DataBind();
         }

      }

      void Item_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Set the SelectedIndex property to select an item in the DataList.
         ItemsList.SelectedIndex = e.Item.ItemIndex;

         // Rebind the data source to the DataList to refresh the control.
         ItemsList.DataSource = CreateDataSource();
         ItemsList.DataBind();

      }

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>DataList Select Example</h3>

      Click <b>Select</b> to select an item.

      <br /><br />

      <asp:DataList id="ItemsList"
           GridLines="Both"
           CellPadding="3"
           CellSpacing="0"           
           OnItemCommand="Item_Command"
           runat="server">

         <HeaderStyle BackColor="#aaaadd">
         </HeaderStyle>

         <AlternatingItemStyle BackColor="Gainsboro">
         </AlternatingItemStyle>

         <SelectedItemStyle BackColor="Yellow">
         </SelectedItemStyle>

         <HeaderTemplate>

            Items

         </HeaderTemplate>

         <ItemTemplate>

            <asp:LinkButton id="SelectButton" 
                 Text="Select" 
                 CommandName="Select"
                 runat="server"/>

            Item <%# DataBinder.Eval(Container.DataItem, "Item") %>

         </ItemTemplate>

         <SelectedItemTemplate>

            Item:
            <asp:Label id="ItemLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Item") %>' 
                 runat="server"/>

            <br />

            Quantity:
            <asp:Label id="QtyLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Qty") %>' 
                 runat="server"/>

            <br />

            Price:
            <asp:Label id="PriceLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>' 
                 runat="server"/>

         </SelectedItemTemplate>

      </asp:DataList>

   </form>

</body>
</html>

Visual Basic

<%@ Page Language="VB" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head>
    <title>DataList Select Example</title>
<script runat="server">

      Function CreateDataSource() As ICollection 

         ' Create sample data for the DataList control.
         Dim dt As DataTable = New DataTable()
         Dim dr As DataRow

         ' Define the columns of the table.
         dt.Columns.Add(New DataColumn("Item", GetType(Int32)))
         dt.Columns.Add(New DataColumn("Qty", GetType(Int32)))
         dt.Columns.Add(New DataColumn("Price", GetType(Double)))

         ' Populate the table with sample values.
         Dim i As Integer

         For i = 0 To 8 

            dr = dt.NewRow()

            dr(0) = i
            dr(1) = i * 2
            dr(2) = 1.23 * (i + 1)

            dt.Rows.Add(dr)

         Next i

         Dim dv As DataView = New DataView(dt)
         Return dv

      End Function

      Sub Page_Load(sender As Object, e As EventArgs) 

         ' Load sample data only once, when the page is first loaded.
         If Not IsPostBack Then 

            ItemsList.DataSource = CreateDataSource()
            ItemsList.DataBind()

         End If

         ' Manually register the event-handling method for the 
         ' ItemCommand event.
         AddHandler ItemsList.ItemCommand, AddressOf Item_Command

      End Sub

      Sub Item_Command(sender As Object, e As DataListCommandEventArgs) 

         ' Set the SelectedIndex property to select an item in the DataList.
         ItemsList.SelectedIndex = e.Item.ItemIndex

         ' Rebind the data source to the DataList to refresh the control.
         ItemsList.DataSource = CreateDataSource()
         ItemsList.DataBind()

      End Sub

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>DataList Select Example</h3>

      Click <b>Select</b> to select an item.

      <br /><br />

      <asp:DataList id="ItemsList"
           GridLines="Both"
           CellPadding="3"
           CellSpacing="0"           
           OnItemCommand="Item_Command"
           runat="server">

         <HeaderStyle BackColor="#aaaadd">
         </HeaderStyle>

         <AlternatingItemStyle BackColor="Gainsboro">
         </AlternatingItemStyle>

         <SelectedItemStyle BackColor="Yellow">
         </SelectedItemStyle>

         <HeaderTemplate>

            Items

         </HeaderTemplate>

         <ItemTemplate>

            <asp:LinkButton id="SelectButton" 
                 Text="Select" 
                 CommandName="Select"
                 runat="server"/>

            Item <%# DataBinder.Eval(Container.DataItem, "Item") %>

         </ItemTemplate>

         <SelectedItemTemplate>

            Item:
            <asp:Label id="ItemLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Item") %>' 
                 runat="server"/>

            <br />

            Quantity:
            <asp:Label id="QtyLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Qty") %>' 
                 runat="server"/>

            <br />

            Price:
            <asp:Label id="PriceLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>' 
                 runat="server"/>

         </SelectedItemTemplate>

      </asp:DataList>

   </form>

</body>
</html>

<%@ Page Language="C#" AutoEventWireup="True" %>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html  >
<head>
    <title>DataList Select Example</title>
<script runat="server">

      ICollection CreateDataSource() 
      {

         // Create sample data for the DataList control.
         DataTable dt = new DataTable();
         DataRow dr;

         // Define the columns of the table.
         dt.Columns.Add(new DataColumn("Item", typeof(Int32)));
         dt.Columns.Add(new DataColumn("Qty", typeof(Int32)));
         dt.Columns.Add(new DataColumn("Price", typeof(double)));

         // Populate the table with sample values.
         for (int i = 0; i < 9; i++) 
         {
            dr = dt.NewRow();

            dr[0] = i;
            dr[1] = i * 2;
            dr[2] = 1.23 * (i + 1);

            dt.Rows.Add(dr);
         }

         DataView dv = new DataView(dt);
         return dv;

      }

      void Page_Load(Object sender, EventArgs e) 
      {

         // Load sample data only once, when the page is first loaded.
         if (!IsPostBack) 
         {
            ItemsList.DataSource = CreateDataSource();
            ItemsList.DataBind();
         }

         // Manually register the event-handling method for the 
         // ItemCommand event.
         ItemsList.ItemCommand += 
             new DataListCommandEventHandler(this.Item_Command);

      }

      void Item_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Set the SelectedIndex property to select an item in the DataList.
         ItemsList.SelectedIndex = e.Item.ItemIndex;

         // Rebind the data source to the DataList to refresh the control.
         ItemsList.DataSource = CreateDataSource();
         ItemsList.DataBind();

      }

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>DataList Select Example</h3>

      Click <b>Select</b> to select an item.

      <br /><br />

      <asp:DataList id="ItemsList"
           GridLines="Both"
           CellPadding="3"
           CellSpacing="0"           
           runat="server">

         <HeaderStyle BackColor="#aaaadd">
         </HeaderStyle>

         <AlternatingItemStyle BackColor="Gainsboro">
         </AlternatingItemStyle>

         <SelectedItemStyle BackColor="Yellow">
         </SelectedItemStyle>

         <HeaderTemplate>

            Items

         </HeaderTemplate>

         <ItemTemplate>

            <asp:LinkButton id="SelectButton" 
                 Text="Select" 
                 CommandName="Select"
                 runat="server"/>

            Item <%# DataBinder.Eval(Container.DataItem, "Item") %>

         </ItemTemplate>

         <SelectedItemTemplate>

            Item:
            <asp:Label id="ItemLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Item") %>' 
                 runat="server"/>

            <br />

            Quantity:
            <asp:Label id="QtyLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Qty") %>' 
                 runat="server"/>

            <br />

            Price:
            <asp:Label id="PriceLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>' 
                 runat="server"/>

         </SelectedItemTemplate>

      </asp:DataList>

   </form>

</body>
</html>

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

Reference

DataList Class

DataList Members

System.Web.UI.WebControls Namespace

ItemCommand

DataListCommandEventArgs

Other Resources

DataList Web Server Control Overview

How to: Consume Events in a Web Forms Application

ASP.NET Web Page Code Model