Esempio di controllo di bubbling degli eventi
Il controllo personalizzato EventBubbler, descritto di seguito, rappresenta un semplice esempio di bubbling degli eventi. EventBubbler è un controllo composto che contiene caselle di testo, pulsanti e un controllo etichetta. EventBubbler passa tramite bubbling gli eventi di comando dai pulsanti al controllo contenitore padre, ovvero a se stesso, e li espone come eventi di primo livello. Per generare l'esempio, vedere le istruzioni in Esempi di controlli server.
Per un esempio pratico, vedere Esempio di controllo basato su template con associazione a dati.
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace CustomControls
{
public class EventBubbler : Control, INamingContainer
{
private int number = 100;
private Label label;
private TextBox box1;
private TextBox box2;
public event EventHandler Click;
public event EventHandler Reset;
public event EventHandler Submit;
public string Label
{
get
{
EnsureChildControls();
return label.Text;
}
set
{
EnsureChildControls();
label.Text = value;
}
}
public int Number
{
get
{
return number;
}
set
{
number = value;
}
}
public string Text1
{
get
{
EnsureChildControls();
return box1.Text;
}
set
{
EnsureChildControls();
box1.Text = value;
}
}
public string Text2
{
get
{
EnsureChildControls();
return box2.Text;
}
set
{
EnsureChildControls();
box2.Text = value;
}
}
protected override void CreateChildControls()
{
Controls.Add(new LiteralControl("<h3>Enter a number : "));
box1 = new TextBox();
box1.Text = "0";
Controls.Add(box1);
Controls.Add(new LiteralControl("</h3>"));
Controls.Add(new LiteralControl("<h3>Enter another number : "));
box2 = new TextBox();
box2.Text = "0";
Controls.Add(box2);
Controls.Add(new LiteralControl("</h3>"));
Button button1 = new Button();
button1.Text = "Click";
button1.CommandName = "Click";
Controls.Add(button1);
Button button2 = new Button();
button2.Text = "Reset";
button2.CommandName = "Reset";
Controls.Add(button2);
Button button3 = new Button();
button3.Text = "Submit";
button3.CommandName = "Submit";
Controls.Add(button3);
Controls.Add(new LiteralControl("<br><br>"));
label = new Label();
label.Height = 50;
label.Width = 500;
label.Text = "Click a button.";
Controls.Add(label);
}
protected override bool OnBubbleEvent(object source, EventArgs e)
{
bool handled = false;
if (e is CommandEventArgs)
{
CommandEventArgs ce = (CommandEventArgs)e;
if (ce.CommandName == "Click")
{
OnClick(ce);
handled = true;
}
else if (ce.CommandName == "Reset")
{
OnReset(ce);
handled = true;
}
else if (ce.CommandName == "Submit")
{
OnSubmit(ce);
handled = true;
}
}
return handled;
}
protected virtual void OnClick (EventArgs e)
{
if (Click != null)
{
Click(this,e);
}
}
protected virtual void OnReset (EventArgs e)
{
if (Reset != null)
{
Reset(this,e);
}
}
protected virtual void OnSubmit (EventArgs e)
{
if (Submit != null)
{
Submit(this,e);
}
}
}
}
[Visual Basic]
Option Explicit
Option Strict
Imports System
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Namespace CustomControls
Public Class EventBubbler
Inherits Control
Implements INamingContainer
Private _number As Integer = 100
Private _label As Label
Private _box1 As TextBox
Private _box2 As TextBox
Public Event Click As EventHandler
Public Event Reset As EventHandler
Public Event Submit As EventHandler
Public Property Label() As String
Get
EnsureChildControls()
Return _label.Text
End Get
Set
EnsureChildControls()
_label.Text = value
End Set
End Property
Public Property Number() As Integer
Get
Return _number
End Get
Set
_number = value
End Set
End Property
Public Property Text1() As String
Get
EnsureChildControls()
Return _box1.Text
End Get
Set
EnsureChildControls()
_box1.Text = value
End Set
End Property
Public Property Text2() As String
Get
EnsureChildControls()
Return _box2.Text
End Get
Set
EnsureChildControls()
_box2.Text = value
End Set
End Property
Protected Overrides Sub CreateChildControls()
Controls.Add(New LiteralControl("<h3>Enter a number : "))
_box1 = New TextBox()
_box1.Text = "0"
Controls.Add(_box1)
Controls.Add(New LiteralControl("</h3>"))
Controls.Add(New LiteralControl("<h3>Enter another number : "))
_box2 = New TextBox()
_box2.Text = "0"
Controls.Add(_box2)
Controls.Add(New LiteralControl("</h3>"))
Dim button1 As New Button()
button1.Text = "Click"
button1.CommandName = "Click"
Controls.Add(button1)
Dim button2 As New Button()
button2.Text = "Reset"
button2.CommandName = "Reset"
Controls.Add(button2)
Dim button3 As New Button()
button3.Text = "Submit"
button3.CommandName = "Submit"
Controls.Add(button3)
Controls.Add(New LiteralControl("<br><br>"))
_label = New Label()
_label.Height = Unit.Pixel(50)
_label.Width = Unit.Pixel(500)
_label.Text = "Click a button."
Controls.Add(_label)
End Sub
Protected Overrides Function OnBubbleEvent(source As Object, e As EventArgs) As Boolean
Dim handled As Boolean = False
If TypeOf e Is CommandEventArgs Then
Dim ce As CommandEventArgs = CType(e, CommandEventArgs)
If ce.CommandName = "Click" Then
OnClick(ce)
handled = True
Else
If ce.CommandName = "Reset" Then
OnReset(ce)
handled = True
Else
If ce.CommandName = "Submit" Then
OnSubmit(ce)
handled = True
End If
End If
End If
End If
Return handled
End Function
Protected Overridable Sub OnClick(e As EventArgs)
RaiseEvent Click(Me, e)
End Sub
Protected Overridable Sub OnReset(e As EventArgs)
RaiseEvent Reset(Me, e)
End Sub
Protected Overridable Sub OnSubmit(e As EventArgs)
RaiseEvent Submit(Me, e)
End Sub
End Class
End Namespace
Utilizzo del controllo per il bubbling degli eventi in una pagina
Nell'esempio di pagina ASP.NET riportato di seguito viene utilizzato il controllo personalizzato per il bubbling degli eventi EventBubbler e vengono connessi i gestori eventi ai relativi eventi di primo livello.
<%@ Register TagPrefix="Custom" Namespace="CustomControls" Assembly = "CustomControls" %>
<html>
<script language="C#" runat=server>
private void ClickHandler(Object sender,EventArgs e)
{
MyControl.Label = "You clicked the <b> Click </b> button";
}
private void ResetHandler(Object sender,EventArgs e)
{
MyControl.Text1 = "0";
MyControl.Text2 = "0";
}
private void SubmitHandler(Object sender,EventArgs e)
{
if ( Int32.Parse(MyControl.Text1) + Int32.Parse(MyControl.Text2) == MyControl.Number)
MyControl.Label = "<h2> You won a million dollars!!!! </h2>";
else
MyControl.Label = "Sorry, try again. The numbers you entered don't add up to" +
" the hidden number.";
}
</script>
<body>
<h1> The Mystery Sum Game </h1><br>
<form runat=server>
<Custom:EventBubbler id = "MyControl" OnClick = "ClickHandler"
OnReset = "ResetHandler" OnSubmit = "SubmitHandler" Number= "10" runat = server/>
</form>
</body>
</html>
[Visual Basic]
<%@ Register TagPrefix="Custom" Namespace="CustomControls" Assembly = "CustomControls" %>
<html>
<script language="VB" runat=server>
Private Sub ClickHandler(sender As Object, e As EventArgs)
MyControl.Label = "You clicked the <b> Click </b> button"
End Sub
Private Sub ResetHandler(sender As Object, e As EventArgs)
MyControl.Text1 = "0"
MyControl.Text2 = "0"
End Sub
Private Sub SubmitHandler(sender As Object, e As EventArgs)
If Int32.Parse(MyControl.Text1) + Int32.Parse(MyControl.Text2) = MyControl.Number Then
MyControl.Label = "<h2> You won a million dollars!!!! </h2>"
Else
MyControl.Label = "Sorry, try again. The numbers you entered don't add up to" & " the hidden number."
End If
End Sub
</script>
<body>
<h1> The Mystery Sum Game </h1><br>
<form runat=server>
<Custom:EventBubbler id = "MyControl" OnClick = "ClickHandler"
OnReset = "ResetHandler" OnSubmit = "SubmitHandler" Number= "10" runat = server/>
</form>
</body>
</html>
Vedere anche
Bubbling di un evento | Esempio di controllo basato su template con associazione a dati