DataGridColumnCollection.AddAt Method (Int32, DataGridColumn)
Inserts a DataGridColumn-derived column object in the DataGridColumnCollection collection at the specified index.
Assembly: System.Web (in System.Web.dll)
Parameters
- index
-
Type:
System.Int32
The index location in the DataGridColumnCollection at which to insert the DataGridColumn-derived column.
- column
-
Type:
System.Web.UI.WebControls.DataGridColumn
The DataGridColumn-derived column to insert in the DataGridColumnCollection.
| Exception | Condition |
|---|---|
| ArgumentNullException | column is null. |
Use this method to insert a DataGridColumn-derived column object at the specified index location in the DataGridColumnCollection collection.
The DataGrid control does not store the contents of its Columns collection in the view state. To add or remove a column dynamically, you must programmatically add or remove the column each time the page is refreshed. Provide a Page_Init function that adds or removes the column before the DataGrid control can reload its state and rebuild itself. Otherwise, the changes to the Columns collection are not reflected in the DataGrid control when it is displayed.
The following code example demonstrates how to use the AddAt method to dynamically add a column to the DataGrid control. Note that the Columns property of the DataGrid control is an instance of the DataGridColumnCollection collection.
<%@ 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 xmlns="http://www.w3.org/1999/xhtml" > <script language="VB" runat="server"> Dim Cart As DataTable Dim CartView As DataView Function CreateDataSource() As ICollection Dim dt As New DataTable() Dim dr As DataRow dt.Columns.Add(New DataColumn("IntegerValue", GetType(Int32))) dt.Columns.Add(New DataColumn("StringValue", GetType(String))) dt.Columns.Add(New DataColumn("CurrencyValue", GetType(Double))) Dim i As Integer For i = 0 To 8 dr = dt.NewRow() dr(0) = i dr(1) = "Item " & i.ToString() dr(2) = 1.23 *(i + 1) dt.Rows.Add(dr) Next i Dim dv As New DataView(dt) Return dv End Function 'CreateDataSource Sub Page_Load(sender As Object, e As EventArgs) If Session("DG4_ShoppingCart") Is Nothing Then Cart = New DataTable() Cart.Columns.Add(New DataColumn("Item", GetType(String))) Cart.Columns.Add(New DataColumn("Price", GetType(String))) Session("DG4_ShoppingCart") = Cart Else Cart = CType(Session("DG4_ShoppingCart"), DataTable) End If CartView = New DataView(Cart) ShoppingCart.DataSource = CartView ShoppingCart.DataBind() If Not IsPostBack Then ' Load this data only once. ItemsGrid.DataSource = CreateDataSource() ItemsGrid.DataBind() End If End Sub 'Page_Load Sub Page_Init(sender As Object, e As EventArgs) ' Create a dynamic column to add to Columns collection. Dim NumberColumn As New BoundColumn() NumberColumn.HeaderText = "Item Number" NumberColumn.DataField = "IntegerValue" ' Add column to Columns collection. ItemsGrid.Columns.AddAt(2, NumberColumn) End Sub 'Page_Init Sub Grid_CartCommand(sender As Object, e As DataGridCommandEventArgs) Dim dr As DataRow = Cart.NewRow() ' e.Item is the table row where the command is raised. ' For bound columns, the value is stored in the Text property of the TableCell. Dim itemCell As TableCell = e.Item.Cells(2) Dim priceCell As TableCell = e.Item.Cells(3) Dim item As String = itemCell.Text Dim price As String = priceCell.Text If CType(e.CommandSource, Button).CommandName = "AddToCart" Then dr(0) = item dr(1) = price Cart.Rows.Add(dr) Else 'Remove from Cart. CartView.RowFilter = "Item='" & item & "'" If CartView.Count > 0 Then CartView.Delete(0) End If CartView.RowFilter = "" End If ShoppingCart.DataBind() End Sub 'Grid_CartCommand </script> <head runat="server"> <title>DataGridColumnCollection AddAt Example</title> </head> <body> <form id="form1" runat="server"> <h3>DataGridColumnCollection AddAt Example</h3> <table cellpadding="5"> <tr valign="top"> <td> <b>Product List</b> <asp:DataGrid id="ItemsGrid" BorderColor="black" BorderWidth="1" CellPadding="3" AutoGenerateColumns="false" OnItemCommand="Grid_CartCommand" runat="server"> <HeaderStyle BackColor="#00aaaa"> </HeaderStyle> <Columns> <asp:ButtonColumn HeaderText="Add to cart" ButtonType="PushButton" Text="Add" CommandName="AddToCart"/> <asp:ButtonColumn HeaderText="Remove from cart" ButtonType="PushButton" Text="Remove" CommandName="RemoveFromCart"/> <asp:BoundColumn HeaderText="Item" DataField="StringValue"/> <asp:BoundColumn HeaderText="Price" DataField="CurrencyValue" DataFormatString="{0:c}"> <ItemStyle HorizontalAlign="right"> </ItemStyle> </asp:BoundColumn> </Columns> </asp:DataGrid> </td> <td> <b>Shopping Cart</b> <asp:DataGrid id="ShoppingCart" runat="server" BorderColor="black" BorderWidth="1" GridLines="Both" ShowFooter="false" CellPadding="3" CellSpacing="0"> <HeaderStyle BackColor="#00aaaa"> </HeaderStyle> </asp:DataGrid> </td> </tr> </table> </form> </body> </html>
Available since 1.1
