DataGridColumnCollection.Remove Method (DataGridColumn)

 

Removes the specified DataGridColumn-derived column object from the DataGridColumnCollection collection.

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

public void Remove(
	DataGridColumn column
)

Parameters

column
Type: System.Web.UI.WebControls.DataGridColumn

The DataGridColumn-derived column to remove from the DataGridColumnCollection.

Use this method to remove the specified DataGridColumn-derived column object from a 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 every 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.

System_CAPS_noteNote

Although you can programmatically add columns to or remove columns from the Columns collection of the DataGrid control, it is easier to list the columns statically and then use the Visible property to display or hide each column.

The following code example demonstrates how to use the Remove method to remove a column from the DataGridColumnCollection collection. Note that the Columns property of the DataGrid control is 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 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();

      }

       void Button_Click(Object sender, EventArgs e) 
      {
         ItemsGrid.Columns.Remove(ItemsGrid.Columns[2]);
      }

   </script>

<head runat="server">
    <title>DataGridColumnCollection Remove Example</title>
</head>
<body>

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

      <h3>DataGridColumnCollection Remove 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 Number" 
                          DataField="IntegerValue"/>

                     <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>

      <asp:Button id="Button1" 
           Text="Remove Item Number Column"
           OnClick="Button_Click"
           runat="server"/>

   </form>

</body>
</html>

.NET Framework
Available since 1.1
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