EventArgs Class

Imports System.Windows.Controls

' FireEventArgs: a custom event inherited from EventArgs.

Public Class FireEventArgs
    Inherits EventArgs

    Public Sub New(ByVal room As String, ByVal ferocity As Integer)
        Me.room = room
        Me.ferocity = ferocity
    End Sub 'New

    ' The fire event will have two pieces of information-- 
    ' 1) Where the fire is, and 2) how "ferocious" it is. 

    Public room As String
    Public ferocity As Integer
End Class


Public Class FireAlarm

    ' Events are handled with delegates, so we must establish a FireEventHandler
    ' as a delegate:

    Delegate Sub FireEventHandler(ByVal sender As Object, ByVal fe As FireEventArgs)

    ' Now, create a public event "FireEvent" whose type is our FireEventHandler delegate.

    Public Event FireEvent As FireEventHandler


    ' This will be the starting point of our event-- it will create FireEventArgs,
    ' and then raise the event, passing FireEventArgs.

    Public Sub ActivateFireAlarm(ByVal room As String, ByVal ferocity As Integer)

        Dim fireArgs As New FireEventArgs(room, ferocity)

        '  Now, raise the event by invoking the delegate. Pass in 
        '  the object that initated the event (Me) as well as FireEventArgs. 
        '  The call must match the signature of FireEventHandler.

        RaiseEvent FireEvent(Me, fireArgs)

    End Sub
End Class

' The following event will be the EventHandler.

Class FireHandlerClass

    Private Shared _TextBlock As TextBlock


    ' Create a FireAlarm to handle and raise the fire events. 

    Public Sub New(ByVal fireAlarm As FireAlarm, ByVal outputBlock As TextBlock)

        ' Add a delegate containing the ExtinguishFire function to the class'
        ' event so that when FireAlarm is raised, it will subsequently execute 
        ' ExtinguishFire.

        AddHandler fireAlarm.FireEvent, AddressOf ExtinguishFire

        FireHandlerClass._TextBlock = outputBlock

    End Sub


    ' This is the function to be executed when a fire event is raised.

    Sub ExtinguishFire(ByVal sender As Object, ByVal fe As FireEventArgs)

        _TextBlock.Text &= vbCrLf
        _TextBlock.Text += String.Format("The ExtinguishFire function was called by {0}.", sender.ToString()) & vbCrLf

        ' Now, act in response to the event.

        If fe.ferocity < 2 Then
            _TextBlock.Text += String.Format("This fire in the {0} is no problem.  I'm going to pour some water on it.", fe.room) & vbCrLf
        Else
            If fe.ferocity < 5 Then
                _TextBlock.Text += String.Format("Using Fire Extinguisher to put out the fire in the {0}.", fe.room) & vbCrLf
            Else
                _TextBlock.Text += String.Format("The fire in the {0} is out of control.  I'm calling the fire department.", fe.room) & vbCrLf
            End If
        End If
    End Sub
End Class

Public Class Example

    Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

        ' Create an instance of the class that will be raising the event.
        Dim myFireAlarm As New FireAlarm()

        ' Create an instance of the class that will be handling the event. Note that 
        ' it receives the class that will fire the event as a parameter. 

        Dim myFireHandler As New FireHandlerClass(myFireAlarm, outputBlock)

        ' Now, use the FireAlarm class to raise a few events. 

        myFireAlarm.ActivateFireAlarm("Kitchen", 3)
        myFireAlarm.ActivateFireAlarm("Study", 1)
        myFireAlarm.ActivateFireAlarm("Porch", 5)

        Return
    End Sub
End Class

using System;
using System.Windows.Controls;

// FireEventArgs: a custom event inherited from EventArgs.

public class FireEventArgs : EventArgs
{
    public FireEventArgs(string room, int ferocity)
    {
        this.room = room;
        this.ferocity = ferocity;
    }

    // The fire event will have two pieces of information--
    // 1) Where the fire is, and 2) how "ferocious" it is.

    public string room;
    public int ferocity;

}


// Class with a function that creates the eventargs and initiates the event
public class FireAlarm
{

    // Events are handled with delegates, so we must establish a FireEventHandler
    // as a delegate:

    public delegate void FireEventHandler(object sender, FireEventArgs fe);

    // Now, create a public event "FireEvent" whose type is our FireEventHandler delegate.

    public event FireEventHandler FireEvent;

    // This will be the starting point of our event-- it will create FireEventArgs,
    // and then raise the event, passing FireEventArgs.

    public void ActivateFireAlarm(string room, int ferocity)
    {

        FireEventArgs fireArgs = new FireEventArgs(room, ferocity);

        // Now, raise the event by invoking the delegate. Pass in
        // the object that initated the event (this) as well as FireEventArgs.
        // The call must match the signature of FireEventHandler.

        FireEvent(this, fireArgs);
    }
}


// Class which handles the event

class FireHandlerClass
{

    private static TextBlock _textblock;


    // Create a FireAlarm to handle and raise the fire events.

    public FireHandlerClass(FireAlarm fireAlarm, TextBlock outputBlock)
    {

        // Add a delegate containing the ExtinguishFire function to the class'
        // event so that when FireAlarm is raised, it will subsequently execute
        // ExtinguishFire.

        fireAlarm.FireEvent += new FireAlarm.FireEventHandler(ExtinguishFire);

        FireHandlerClass._textblock = outputBlock;

    }

    // This is the function to be executed when a fire event is raised.

    void ExtinguishFire(object sender, FireEventArgs fe)
    {

        _textblock.Text += String.Format("\nThe ExtinguishFire function was called by {0}.", sender.ToString()) + "\n";

        // Now, act in response to the event.

        if (fe.ferocity < 2)
            _textblock.Text += String.Format("This fire in the {0} is no problem.  I'm going to pour some water on it.", fe.room) + "\n";
        else if (fe.ferocity < 5)
            _textblock.Text += String.Format("I'm using FireExtinguisher to put out the fire in the {0}.", fe.room) + "\n";
        else
            _textblock.Text += String.Format("The fire in the {0} is out of control.  I'm calling the fire department!", fe.room) + "\n";
    }
}

public class Example
{
    public static void Demo(System.Windows.Controls.TextBlock outputBlock)
    {

        // Create an instance of the class that will be firing an event.

        FireAlarm myFireAlarm = new FireAlarm();

        // Create an instance of the class that will be handling the event. Note that
        // it receives the class that will fire the event as a parameter.

        FireHandlerClass myFireHandler = new FireHandlerClass(myFireAlarm, outputBlock);

        //use our class to raise a few events and watch them get handled
        myFireAlarm.ActivateFireAlarm("Kitchen", 3);
        myFireAlarm.ActivateFireAlarm("Study", 1);
        myFireAlarm.ActivateFireAlarm("Porch", 5);

        return;

    }

}