DataGridColumnCollection.Clear Método
Definição
Importante
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Remove todos os objetos de coluna derivados de DataGridColumn da coleção DataGridColumnCollection.
public:
void Clear();public void Clear ();member this.Clear : unit -> unitPublic Sub Clear ()Exemplos
O exemplo de código a seguir demonstra como usar o Clear método para esvaziar a DataGridColumnCollection coleção antes de adicionar novas colunas à 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">
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_Init(Object sender, EventArgs e)
{
// Empty DataGridColumnsCollection collection.
ItemsGrid.Columns.Clear();
// Create dynamic columns to add to Columns collection.
BoundColumn IntegerColumn = new BoundColumn();
BoundColumn StringColumn = new BoundColumn();
BoundColumn PriceColumn = new BoundColumn();
IntegerColumn.HeaderText="Item Number";
IntegerColumn.DataField="IntegerValue";
StringColumn.HeaderText="Item";
StringColumn.DataField="StringValue";
PriceColumn.HeaderText="Price";
PriceColumn.DataField="CurrencyValue";
// Add columns to Columns collection.
ItemsGrid.Columns.Add(IntegerColumn);
ItemsGrid.Columns.Add(StringColumn);
ItemsGrid.Columns.Add(PriceColumn);
}
void Page_Load(Object sender, EventArgs e)
{
if (!IsPostBack)
{
// Load this data only once.
ItemsGrid.DataSource= CreateDataSource();
ItemsGrid.DataBind();
}
}
</script>
<head runat="server">
<title>DataGridColumnCollection Clear Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>DataGridColumnCollection Clear Example</h3>
<b>Product List</b>
<asp:DataGrid id="ItemsGrid"
BorderColor="black"
BorderWidth="1"
CellPadding="3"
AutoGenerateColumns="false"
runat="server">
<HeaderStyle BackColor="#00aaaa">
</HeaderStyle>
<Columns>
<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>
</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">
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_Init(sender As Object, e As EventArgs)
' Empty DataGridColumnsCollection collection.
ItemsGrid.Columns.Clear()
' Create dynamic columns to add to Columns collection.
Dim IntegerColumn As New BoundColumn()
Dim StringColumn As New BoundColumn()
Dim PriceColumn As New BoundColumn()
IntegerColumn.HeaderText = "Item Number"
IntegerColumn.DataField = "IntegerValue"
StringColumn.HeaderText = "Item"
StringColumn.DataField = "StringValue"
PriceColumn.HeaderText = "Price"
PriceColumn.DataField = "CurrencyValue"
' Add columns to Columns collection.
ItemsGrid.Columns.Add(IntegerColumn)
ItemsGrid.Columns.Add(StringColumn)
ItemsGrid.Columns.Add(PriceColumn)
End Sub 'Page_Init
Sub Page_Load(sender As Object, e As EventArgs)
If Not IsPostBack Then
' Load this data only once
ItemsGrid.DataSource = CreateDataSource()
ItemsGrid.DataBind()
End If
End Sub 'Page_Load
</script>
<head runat="server">
<title>DataGridColumnCollection Clear Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>DataGridColumnCollection Clear Example</h3>
<b>Product List</b>
<asp:DataGrid id="ItemsGrid"
BorderColor="black"
BorderWidth="1"
CellPadding="3"
AutoGenerateColumns="false"
runat="server">
<HeaderStyle BackColor="#00aaaa">
</HeaderStyle>
<Columns>
<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>
</form>
</body>
</html>
Comentários
Use esse método para remover todos os DataGridColumnobjetos de coluna derivados da DataGridColumnCollection coleção.
Observação
A Count propriedade é definida automaticamente depois que 0 esse método é usado.