Export (0) Print
Expand All
Expand Minimize

ConsoleCancelEventHandler Delegate

Represents the method that will handle the CancelKeyPress event of a System.Console.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

'Declaration
Public Delegate Sub ConsoleCancelEventHandler ( _
	sender As Object, _
	e As ConsoleCancelEventArgs _
)
'Usage
Dim instance As New ConsoleCancelEventHandler(AddressOf HandlerMethod)
/** @delegate */
public delegate void ConsoleCancelEventHandler (
	Object sender, 
	ConsoleCancelEventArgs e
)
Not applicable.

Parameters

sender

The source of the event.

e

A System.ConsoleCancelEventArgs object that contains the event data.

When you create a ConsoleCancelEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see Events and Delegates.

The following code example demonstrates how to use the ConsoleCancelEventHandler class to handle an event.

' This example demonstrates:
' the Console.CancelKeyPress event,
' the ConsoleCancelEventHandler delegate, 
' the ConsoleCancelEventArgs.SpecialKey property, and 
' the ConsoleCancelEventArgs.Cancel property.

Imports System

Class Sample
    Public Shared Sub Main() 
        Dim cki As ConsoleKeyInfo
        
        ' Clear the screen.
        Console.Clear()
        
        ' Turn off the default system behavior when CTRL+C is pressed. When 
        ' Console.TreatControlCAsInput is false, CTRL+C is treated as an
        ' interrupt instead of as input.
        Console.TreatControlCAsInput = False
        
        ' Establish an event handler to process key press events.
        AddHandler Console.CancelKeyPress, AddressOf myHandler

        While True
            ' Prompt the user.
            Console.Write("Press any key, or 'X' to quit, or ")
            Console.WriteLine("CTRL+C to interrupt the read operation:")
            
            ' Start a console read operation. Do not display the input.
            cki = Console.ReadKey(True)
            
            ' Announce the name of the key that was pressed .
            Console.WriteLine("  Key pressed: {0}" & vbCrLf, cki.Key)
            
            ' Exit if the user pressed the 'X' key.
            If cki.Key = ConsoleKey.X Then Exit While
        End While
    End Sub 'Main
     
'   When you press CTRL+C, the read operation is interrupted and the 
'   console cancel event handler, myHandler, is invoked. Upon entry 
'   to the event handler, the Cancel property is false, which means 
'   the current process will terminate when the event handler terminates. 
'   However, the event handler sets the Cancel property to true, which 
'   means the process will not terminate and the read operation will resume.

    Protected Shared Sub myHandler(ByVal sender As Object, _
                                   ByVal args As ConsoleCancelEventArgs) 
        ' Announce that the event handler has been invoked.
        Console.WriteLine(vbCrLf & "The read operation has been interrupted.")
        
        ' Announce which key combination was pressed.
        Console.WriteLine("  Key pressed: {0}", args.SpecialKey)
        
        ' Announce the initial value of the Cancel property.
        Console.WriteLine("  Cancel property: {0}", args.Cancel)
        
        ' Set the Cancel property to true to prevent the process from terminating.
        Console.WriteLine("Setting the Cancel property to true...")
        args.Cancel = True
        
        ' Announce the new value of the Cancel property.
        Console.WriteLine("  Cancel property: {0}", args.Cancel)
        Console.WriteLine("The read operation will resume..." & vbCrLf)
    
    End Sub 'myHandler
End Class 'Sample
'
'This code example produces results similar to the following text:
'
'Press any key, or 'X' to quit, or CTRL+C to interrupt the read operation:
'  Key pressed: J
'
'Press any key, or 'X' to quit, or CTRL+C to interrupt the read operation:
'  Key pressed: Enter
'
'Press any key, or 'X' to quit, or CTRL+C to interrupt the read operation:
'
'The read operation has been interrupted.
'  Key pressed: ControlC
'  Cancel property: False
'Setting the Cancel property to true...
'  Cancel property: True
'The read operation will resume...
'
'  Key pressed: Q
'
'Press any key, or 'X' to quit, or CTRL+C to interrupt the read operation:
'  Key pressed: X
'

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

Community Additions

ADD
Show:
© 2014 Microsoft