GridView.Sorting Evento
Definizione
Importante
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Si verifica quando viene fatto clic sul collegamento ipertestuale per l'ordinamento di una colonna, ma prima che il controllo GridView gestisca l'operazione di ordinamento.
public:
event System::Web::UI::WebControls::GridViewSortEventHandler ^ Sorting;public event System.Web.UI.WebControls.GridViewSortEventHandler Sorting;member this.Sorting : System.Web.UI.WebControls.GridViewSortEventHandler Public Custom Event Sorting As GridViewSortEventHandler Tipo evento
Esempio
Nell'esempio seguente viene illustrato come utilizzare l'evento Sorting per eseguire la funzionalità di ordinamento quando il GridView controllo è associato a un DataTable oggetto impostando la DataSource proprietà a livello di codice.
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void TaskGridView_Sorting(object sender, GridViewSortEventArgs e)
{
//Retrieve the table from the session object.
DataTable dt = Session["TaskTable"] as DataTable;
if (dt != null)
{
//Sort the data.
dt.DefaultView.Sort = e.SortExpression + " " + GetSortDirection(e.SortExpression);
TaskGridView.DataSource = Session["TaskTable"];
TaskGridView.DataBind();
}
}
private string GetSortDirection(string column)
{
// By default, set the sort direction to ascending.
string sortDirection = "ASC";
// Retrieve the last column that was sorted.
string sortExpression = ViewState["SortExpression"] as string;
if (sortExpression != null)
{
// Check if the same column is being sorted.
// Otherwise, the default value can be returned.
if (sortExpression == column)
{
string lastDirection = ViewState["SortDirection"] as string;
if ((lastDirection != null) && (lastDirection == "ASC"))
{
sortDirection = "DESC";
}
}
}
// Save new values in ViewState.
ViewState["SortDirection"] = sortDirection;
ViewState["SortExpression"] = column;
return sortDirection;
}
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
// Create a new table.
DataTable taskTable = new DataTable("TaskList");
// Create the columns.
taskTable.Columns.Add("Id", typeof(int));
taskTable.Columns.Add("Description", typeof(string));
//Add data to the new table.
for (int i = 0; i < 10; i++)
{
DataRow tableRow = taskTable.NewRow();
tableRow["Id"] = i;
tableRow["Description"] = "Task " + (10 - i).ToString();
taskTable.Rows.Add(tableRow);
}
//Persist the table in the Session object.
Session["TaskTable"] = taskTable;
//Bind the GridView control to the data source.
TaskGridView.DataSource = Session["TaskTable"];
TaskGridView.DataBind();
}
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Sorting example</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="TaskGridView" runat="server"
AllowSorting="true"
OnSorting="TaskGridView_Sorting" >
</asp:GridView>
</div>
</form>
</body>
</html>
<%@ Page Language="VB" %>
<%@ Import Namespace="System.Data" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub TaskGridView_Sorting(ByVal sender As Object, ByVal e As GridViewSortEventArgs)
'Retrieve the table from the session object.
Dim dt = TryCast(Session("TaskTable"), DataTable)
If dt IsNot Nothing Then
'Sort the data.
dt.DefaultView.Sort = e.SortExpression & " " & GetSortDirection(e.SortExpression)
TaskGridView.DataSource = Session("TaskTable")
TaskGridView.DataBind()
End If
End Sub
Private Function GetSortDirection(ByVal column As String) As String
' By default, set the sort direction to ascending.
Dim sortDirection = "ASC"
' Retrieve the last column that was sorted.
Dim sortExpression = TryCast(ViewState("SortExpression"), String)
If sortExpression IsNot Nothing Then
' Check if the same column is being sorted.
' Otherwise, the default value can be returned.
If sortExpression = column Then
Dim lastDirection = TryCast(ViewState("SortDirection"), String)
If lastDirection IsNot Nothing _
AndAlso lastDirection = "ASC" Then
sortDirection = "DESC"
End If
End If
End If
' Save new values in ViewState.
ViewState("SortDirection") = sortDirection
ViewState("SortExpression") = column
Return sortDirection
End Function
Protected Sub Page_Load()
If Not Page.IsPostBack Then
' Create a new table.
Dim taskTable As New DataTable("TaskList")
' Create the columns.
taskTable.Columns.Add("Id", GetType(Integer))
taskTable.Columns.Add("Description", GetType(String))
'Add data to the new table.
For i = 0 To 9
Dim tableRow As DataRow = taskTable.NewRow()
tableRow("Id") = i
tableRow("Description") = "Task " & (10 - i)
taskTable.Rows.Add(tableRow)
Next i
'Persist the table in the Session object.
Session("TaskTable") = taskTable
'Bind the GridView control to the data source.
TaskGridView.DataSource = Session("TaskTable")
TaskGridView.DataBind()
End If
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Sorting example</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="TaskGridView" runat="server"
AllowSorting="true"
OnSorting="TaskGridView_Sorting" >
</asp:GridView>
</div>
</form>
</body>
</html>
Nell'esempio seguente viene illustrato come utilizzare l'evento Sorting per annullare un'operazione di ordinamento.
<%@ Page language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
void CustomersGridView_Sorting(Object sender, GridViewSortEventArgs e)
{
// Cancel the sorting operation if the user attempts
// to sort by address.
if (e.SortExpression == "Address")
{
e.Cancel = true;
Message.Text = "You cannot sort by address.";
SortInformationLabel.Text = "";
}
else
{
Message.Text = "";
}
}
void CustomersGridView_Sorted(Object sender, EventArgs e)
{
// Display the sort expression and sort direction.
SortInformationLabel.Text = "Sorting by " +
CustomersGridView.SortExpression.ToString() +
" in " + CustomersGridView.SortDirection.ToString() +
" order.";
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>GridView Sorting Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>GridView Sorting Example</h3>
<asp:label id="Message"
forecolor="Red"
runat="server"/>
<br/>
<asp:label id="SortInformationLabel"
forecolor="Navy"
runat="server"/>
<br/>
<asp:gridview id="CustomersGridView"
datasourceid="CustomersSource"
autogeneratecolumns="true"
allowpaging="true"
emptydatatext="No data available."
allowsorting="true"
onsorting="CustomersGridView_Sorting"
onsorted="CustomersGridView_Sorted"
runat="server">
</asp:gridview>
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the Northwind sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:sqldatasource id="CustomersSource"
selectcommand="Select [CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country] From [Customers]"
connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
runat="server"/>
</form>
</body>
</html>
<%@ Page language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Sub CustomersGridView_Sorting(sender As Object, e As GridViewSortEventArgs)
' Cancel the sorting operation if the user attempts
' to sort by address.
If e.SortExpression = "Address" Then
e.Cancel = True
Message.Text = "You cannot sort by address."
SortInformationLabel.Text = ""
Else
Message.Text = ""
End If
End Sub
Sub CustomersGridView_Sorted(ByVal sender As Object, ByVal e As EventArgs)
' Display the sort expression and sort direction.
SortInformationLabel.Text = "Sorting by " & _
CustomersGridView.SortExpression.ToString() & _
" in " & CustomersGridView.SortDirection.ToString() & _
" order."
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>GridView Sorted and Sorting Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>GridView Sorted and Sorting Example</h3>
<asp:label id="Message"
forecolor="Red"
runat="server"/>
<br/>
<asp:label id="SortInformationLabel"
forecolor="Navy"
runat="server"/>
<br/>
<asp:gridview id="CustomersGridView"
datasourceid="CustomersSource"
autogeneratecolumns="true"
allowpaging="true"
emptydatatext="No data available."
allowsorting="true"
onsorting="CustomersGridView_Sorting"
onsorted="CustomersGridView_Sorted"
runat="server">
</asp:gridview>
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the Northwind sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:sqldatasource id="CustomersSource"
selectcommand="Select [CustomerID], [CompanyName], [Address], [City], [PostalCode], [Country] From [Customers]"
connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
runat="server"/>
</form>
</body>
</html>
Commenti
L'evento Sorting viene generato quando si fa clic sul collegamento ipertestuale per ordinare una colonna, ma prima che il GridView controllo gestisca l'operazione di ordinamento. In questo modo è possibile fornire un metodo di gestione degli eventi che esegue una routine personalizzata, ad esempio l'annullamento dell'operazione di ordinamento, ogni volta che si verifica questo evento.
Un GridViewSortEventArgs oggetto viene passato al metodo di gestione degli eventi, che consente di determinare l'espressione di ordinamento per la colonna e di indicare che l'operazione di selezione deve essere annullata. Per annullare l'operazione di selezione, impostare la Cancel proprietà dell'oggetto GridViewSortEventArgs su true.
Per informazioni su come avviare un'operazione di ordinamento a livello di codice, vedere il Sort metodo .
Per altre informazioni su come gestire gli eventi, vedere la gestione e generazione di eventi.
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