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DataGridColumnCollection.Remove(DataGridColumn) Metodo

Definizione

Rimuove l'oggetto colonna derivato da DataGridColumn specificato dall'insieme DataGridColumnCollection.

public:
 void Remove(System::Web::UI::WebControls::DataGridColumn ^ column);
public void Remove (System.Web.UI.WebControls.DataGridColumn column);
member this.Remove : System.Web.UI.WebControls.DataGridColumn -> unit
Public Sub Remove (column As DataGridColumn)

Parametri

column
DataGridColumn

Colonna derivata da DataGridColumn da rimuovere dall'insieme DataGridColumnCollection.

Esempio

Nell'esempio di codice seguente viene illustrato come utilizzare il Remove metodo per rimuovere una colonna dalla DataGridColumnCollection raccolta. Si noti che la Columns proprietà del DataGrid controllo è l'insieme DataGridColumnCollection .

<%@ 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>
<%@ 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 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
         

        Sub Button_Click(sender As Object, e As EventArgs)
            ItemsGrid.Columns.Remove(ItemsGrid.Columns(2))
        End Sub 'Button_Click
 
   </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>

Commenti

Utilizzare questo metodo per rimuovere l'oggetto colonna derivato da un DataGridColumnCollection insieme specificatoDataGridColumn.

Il DataGrid controllo non archivia il contenuto della raccolta Columns nello stato di visualizzazione. Per aggiungere o rimuovere una colonna in modo dinamico, è necessario aggiungere o rimuovere la colonna a livello di codice ogni volta che la pagina viene aggiornata. Specificare una Page_Init funzione che aggiunge o rimuove la colonna prima che il DataGrid controllo possa ricaricare lo stato e ricompilarsi. In caso contrario, le modifiche apportate alla Columns raccolta non vengono riflesse nel DataGrid controllo quando viene visualizzato.

Nota

Sebbene sia possibile aggiungere o rimuovere colonne a livello di codice dall'insieme Columns del DataGrid controllo, è più semplice elencare le colonne in modo statico e quindi usare la Visible proprietà per visualizzare o nascondere ogni colonna.

Si applica a

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