Event Bubbling Control Sample
.NET Framework 1.1
The following custom control, EventBubbler, demonstrates a simple case of event bubbling. EventBubbler is a composite control that contains text boxes, buttons, and a label control. EventBubbler bubbles the command events from the buttons to the parent container control (itself) and exposes them as top-level events. To build the sample, see the instructions in Server Control Samples.
For a more realistic example, see the Templated Data-Bound Control Sample.
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
Using the Event Bubbling Control on a Page
The following ASP.NET page uses the custom event bubbling control EventBubbler and attaches event handlers to its top-level events.
<%@ 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>