DataGridColumnCollection.RemoveAt(Int32) Método
Definição
Importante
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Remove um objeto de coluna derivado de DataGridColumn da coleção DataGridColumnCollection no índice especificado.
public:
void RemoveAt(int index);public void RemoveAt (int index);member this.RemoveAt : int -> unitPublic Sub RemoveAt (index As Integer)Parâmetros
- index
- Int32
O índice da coluna derivada de DataGridColumn no DataGridColumnCollection a remover.
Exceções
index é menor que 0 ou maior que Count.
Exemplos
O exemplo de código a seguir demonstra como usar o RemoveAt método para remover uma coluna da DataGridColumnCollection coleção. Observe que a Columns propriedade do DataGrid controle é a DataGridColumnCollection coleção.
<%@ 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 Page_Init(Object sender, EventArgs e)
{
ItemsGrid.Columns.RemoveAt(2);
}
</script>
<head runat="server">
<title>DataGridColumnCollection RemoveAt Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>DataGridColumnCollection RemoveAt 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>
</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 Page_Init(sender As Object, e As EventArgs)
ItemsGrid.Columns.RemoveAt(2)
End Sub 'Page_Init
</script>
<head runat="server">
<title>DataGridColumnCollection RemoveAt Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>DataGridColumnCollection RemoveAt 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>
</form>
</body>
</html>
Comentários
Use esse método para remover um DataGridColumnobjeto de coluna derivado de uma DataGridColumnCollection coleção no índice especificado.
O DataGrid controle não armazena o conteúdo de sua Columns coleção no estado de exibição. Para adicionar ou remover uma coluna dinamicamente, você deve adicionar ou remover a coluna programaticamente sempre que a página for atualizada. Forneça uma Page_Init função que adicione ou remova a coluna antes que o DataGrid controle possa recarregar seu estado e se recompilar. Caso contrário, as alterações na Columns coleção não são refletidas no DataGrid controle quando ela é exibida.
Observação
Embora você possa adicionar colunas programaticamente ou remover colunas da Columns coleção do DataGrid controle, é mais fácil listar as colunas estaticamente e, em seguida, usar a Visible propriedade para exibir ou ocultar cada coluna.