TreeNodeEventHandler Delegato
Importante
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Rappresenta il metodo che gestirà l'evento TreeNodeCollapsed, TreeNodeDataBound, TreeNodeExpanded, oppure TreeNodePopulate del controllo TreeView.
public delegate void TreeNodeEventHandler(System::Object ^ sender, TreeNodeEventArgs ^ e);
public delegate void TreeNodeEventHandler(object sender, TreeNodeEventArgs e);
type TreeNodeEventHandler = delegate of obj * TreeNodeEventArgs -> unit
Public Delegate Sub TreeNodeEventHandler(sender As Object, e As TreeNodeEventArgs)
- sender
- Object
Origine dell'evento.
Oggetto TreeNodeEventArgs che contiene i dati dell'evento.
Nell'esempio di codice seguente viene illustrato come usare il TreeNodeEventHandler delegato per registrare un metodo di gestione eventi a livello di codice.
<%@ 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 Page_Load(Object sender, EventArgs e)
{
// Create a new TreeView control.
TreeView NewTree = new TreeView();
// Set the properties of the TreeView control.
NewTree.ID = "BookTreeView";
NewTree.DataSourceID = "BookXmlDataSource";
// Create the tree node binding relationship.
// Create the root node binding.
TreeNodeBinding RootBinding = new TreeNodeBinding();
RootBinding.DataMember = "Book";
RootBinding.TextField = "Title";
// Create the parent node binding.
TreeNodeBinding ParentBinding = new TreeNodeBinding();
ParentBinding.DataMember = "Chapter";
ParentBinding.TextField = "Heading";
// Create the leaf node binding.
TreeNodeBinding LeafBinding = new TreeNodeBinding();
LeafBinding.DataMember = "Section";
LeafBinding.TextField = "Heading";
// Add bindings to the DataBindings collection.
NewTree.DataBindings.Add(RootBinding);
NewTree.DataBindings.Add(ParentBinding);
NewTree.DataBindings.Add(LeafBinding);
// Manually register the event handler for the TreeNodeExpanded event.
NewTree.TreeNodeExpanded += new TreeNodeEventHandler(this.Node_Expand);
// Add the TreeView control to the Controls collection of the PlaceHolder control.
ControlPlaceHolder.Controls.Add(NewTree);
}
void Node_Expand(Object sender, TreeNodeEventArgs e)
{
// Display the expanded node.
Message.Text = "You expanded: " + e.Node.Text;
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>TreeView TreeNodeEventHandler Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>TreeView TreeNodeEventHandler Example</h3>
<asp:PlaceHolder id="ControlPlaceHolder" runat="server">
</asp:PlaceHolder>
<asp:XmlDataSource id="BookXmlDataSource"
DataFile="book.xml"
runat="server">
</asp:XmlDataSource>
<br /><br />
<asp:Label id="Message" 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 Page_Load(ByVal sender As Object, ByVal e As EventArgs)
' Create a new TreeView control.
Dim NewTree As TreeView = New TreeView
' Set the properties of the TreeView control.
NewTree.ID = "BookTreeView"
NewTree.DataSourceID = "BookXmlDataSource"
' Create the tree node binding relationship.
' Create the root node binding.
Dim RootBinding As TreeNodeBinding = New TreeNodeBinding
RootBinding.DataMember = "Book"
RootBinding.TextField = "Title"
' Create the parent node binding.
Dim ParentBinding As TreeNodeBinding = New TreeNodeBinding
ParentBinding.DataMember = "Chapter"
ParentBinding.TextField = "Heading"
' Create the leaf node binding.
Dim LeafBinding As TreeNodeBinding = New TreeNodeBinding
LeafBinding.DataMember = "Section"
LeafBinding.TextField = "Heading"
' Add bindings to the DataBindings collection.
NewTree.DataBindings.Add(RootBinding)
NewTree.DataBindings.Add(ParentBinding)
NewTree.DataBindings.Add(LeafBinding)
' Manually register the event handler for the TreeNodeExpanded event.
AddHandler NewTree.TreeNodeExpanded, AddressOf Node_Expand
' Add the TreeView control to the Controls collection of the PlaceHolder control.
ControlPlaceHolder.Controls.Add(NewTree)
End Sub
Sub Node_Expand(ByVal sender As Object, ByVal e As TreeNodeEventArgs)
' Display the expanded node.
Message.Text = "You expanded: " & e.Node.Text
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>TreeView TreeNodeEventHandler Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>TreeView TreeNodeEventHandler Example</h3>
<asp:PlaceHolder id="ControlPlaceHolder" runat="server">
</asp:PlaceHolder>
<asp:XmlDataSource id="BookXmlDataSource"
DataFile="book.xml"
runat="server">
</asp:XmlDataSource>
<br /><br />
<asp:Label id="Message" runat="server"/>
</form>
</body>
</html>
Quando si crea un delegato TreeNodeEventHandler, si identifica il metodo che gestirà l'evento. Per associare l'evento al gestore eventi in uso, aggiungere all'evento un'istanza del delegato. Il gestore eventi viene chiamato ogni volta che si verifica l'evento, a meno che non venga rimosso il delegato. Per altre informazioni sui delegati del gestore eventi, vedere Gestione e generazione di eventi.
Get |
Ottiene un oggetto che rappresenta il metodo rappresentato dal delegato specificato. |
Prodotto | Versioni |
---|---|
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
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