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="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 xmlns="http://www.w3.org/1999/xhtml" > <script language="C#" runat="server"> DataTable Cart; DataView CartView; ICollection CreateDataSource() { DataTable dt = new DataTable(); DataRow dr; dt.Columns.Add(new DataColumn("IntegerValue", typeof(Int32))); dt.Columns.Add(new DataColumn("StringValue", typeof(string))); dt.Columns.Add(new DataColumn("CurrencyValue", typeof(double))); for (int i = 0; i < 9; i++) { dr = dt.NewRow(); dr[0] = i; dr[1] = "Item " + i.ToString(); dr[2] = 1.23 * (i + 1); dt.Rows.Add(dr); } DataView dv = new DataView(dt); return dv; } void Page_Load(Object sender, EventArgs e) { if (Session["DG4_ShoppingCart"] == null) { Cart = new DataTable(); Cart.Columns.Add(new DataColumn("Item", typeof(string))); Cart.Columns.Add(new DataColumn("Price", typeof(string))); Session["DG4_ShoppingCart"] = Cart; } else { Cart = (DataTable)Session["DG4_ShoppingCart"]; } CartView = new DataView(Cart); ShoppingCart.DataSource = CartView; ShoppingCart.DataBind(); if (!IsPostBack) { // Load this data only once. ItemsGrid.DataSource= CreateDataSource(); ItemsGrid.DataBind(); } } void Page_Init(Object sender, EventArgs e) { // Create a dynamic column to add to Columns collection. BoundColumn NumberColumn = new BoundColumn(); NumberColumn.HeaderText="Item Number"; NumberColumn.DataField="IntegerValue"; // Add column to Columns collection. ItemsGrid.Columns.AddAt(2, NumberColumn); } void Grid_CartCommand(Object sender, DataGridCommandEventArgs e) { DataRow dr = 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. TableCell itemCell = e.Item.Cells[2]; TableCell priceCell = e.Item.Cells[3]; string item = itemCell.Text; string price = priceCell.Text; if (((Button)e.CommandSource).CommandName == "AddToCart") { dr[0] = item; dr[1] = price; Cart.Rows.Add(dr); } else { //Remove from Cart. CartView.RowFilter = "Item='" + item + "'"; if (CartView.Count > 0) { CartView.Delete(0); } CartView.RowFilter = ""; } ShoppingCart.DataBind(); } </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
