ConsoleCancelEventArgs.Cancel Property

Definition

获取或设置一个值,该值指示同时按下 Control 修改键和 C 控制台键 (Ctrl+C) 或 Ctrl+Break 键是否会终止当前进程。Gets or sets a value that indicates whether simultaneously pressing the Control modifier key and the C console key (Ctrl+C) or the Ctrl+Break keys terminates the current process. 默认值为 false,这将终止当前进程。The default is false, which terminates the current process.

public:
 property bool Cancel { bool get(); void set(bool value); };
public bool Cancel { get; set; }
member this.Cancel : bool with get, set
Public Property Cancel As Boolean

Property Value

Boolean

如果当前进程在事件处理程序结束时应继续,则为 true;如果当前进程应终止,则为 falsetrue if the current process should resume when the event handler concludes; false if the current process should terminate. 默认值为 false;当前进程将在事件处理程序返回时终止。The default value is false; the current process terminates when the event handler returns. 如果为 true,当前进程将继续。If true, the current process continues.

Examples

下面的示例演示如何使用 Cancel 属性来处理事件。The following example demonstrates how to use the Cancel property to handle an event.

using namespace System;

void OnCancelKeyPressed(Object^ sender, 
    ConsoleCancelEventArgs^ args)
{
    Console::WriteLine("{0}The read operation has been interrupted.",
        Environment::NewLine);

    Console::WriteLine("  Key pressed: {0}", args->SpecialKey);

    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...{0}",
        Environment::NewLine);
}

int main()
{       
    // Clear the screen.
    Console::Clear();

    // Establish an event handler to process key press events.
    Console::CancelKeyPress += 
        gcnew ConsoleCancelEventHandler(OnCancelKeyPressed);

    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.
        ConsoleKeyInfo^ keyInfo = Console::ReadKey(true);

        // Announce the name of the key that was pressed .
        Console::WriteLine("  Key pressed: {0}{1}", keyInfo->Key, 
            Environment::NewLine);

        // Exit if the user pressed the 'X' key.
        if (keyInfo->Key == ConsoleKey::X)
        {
            break;
        }
    }
}
// The example displays output similar to the following:
//    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
using System;

class Sample
{
    public static void Main()
    {
        ConsoleKeyInfo cki;

        Console.Clear();

        // Establish an event handler to process key press events.
        Console.CancelKeyPress += new ConsoleCancelEventHandler(myHandler);
        while (true)
        {
            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: {cki.Key}\n");

            // Exit if the user pressed the 'X' key.
            if (cki.Key == ConsoleKey.X) break;
        }
    }

    protected static void myHandler(object sender, ConsoleCancelEventArgs args)
    {
        Console.WriteLine("\nThe read operation has been interrupted.");

        Console.WriteLine($"  Key pressed: {args.SpecialKey}");

        Console.WriteLine($"  Cancel property: {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: {args.Cancel}");
        Console.WriteLine("The read operation will resume...\n");
    }
}
// The example displays output similar to the following:
//    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
Class Sample
    Public Shared Sub Main() 
        Dim cki As ConsoleKeyInfo
        
        Console.Clear()
        
        ' Establish an event handler to process key press events.
        AddHandler Console.CancelKeyPress, AddressOf myHandler

        While True
            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: {cki.Key}{vbCrLf}")
            
            ' Exit if the user pressed the 'X' key.
            If cki.Key = ConsoleKey.X Then Exit While
        End While
    End Sub

    Protected Shared Sub myHandler(ByVal sender As Object, _
                                   ByVal args As ConsoleCancelEventArgs) 
        Console.WriteLine($"{vbCrLf}The read operation has been interrupted.")
        
        Console.WriteLine($"  Key pressed: {args.SpecialKey}")
        
        Console.WriteLine($"  Cancel property: {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($"  Cancel property: {args.Cancel}")
        Console.WriteLine($"The read operation will resume...{vbCrLf}")
    End Sub
End Class
' The example diplays output similar to the following:
'    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

Remarks

当调用 CancelKeyPress 事件的处理程序时,Cancel 属性将自动初始化为 falseThe Cancel property is automatically initialized to false when the handler for the CancelKeyPress event is invoked. 当事件处理程序完成时,Cancel 属性的值将确定当前进程是恢复还是终止。The value of the Cancel property when the event handler finishes determines whether the current process resumes or terminates.

在按下 Ctrl + C 后,在设置操作中,指定 true 以指示当前进程应在事件处理程序结束时恢复,或 false 以指示当前进程应终止。In a set operation after Ctrl+C is pressed, specify true to indicate that the current process should resume when the event handler concludes, or false to indicate that the current process should terminate.

Notes to Callers

.NET Framework 3.5.NET Framework 3.5.NET Framework 4.NET Framework 4中,尝试将 Cancel 属性设置为 true 如果用户按下 Ctrl + Break 调用了 CancelKeyPress 事件,按 Ctrl + Break 引发了 InvalidOperationException 异常。In the .NET Framework 3.5.NET Framework 3.5 and .NET Framework 4.NET Framework 4, attempting to set the Cancel property to true if the CancelKeyPress event was invoked by the user pressing Ctrl+Break threw an InvalidOperationException exception. .NET Framework 4.5.NET Framework 4.5中,你可以将 Cancel 属性设置为在用户按下 Ctrl + Break 后 true,并取消应用程序终止。In the .NET Framework 4.5.NET Framework 4.5, you can set the Cancel property to true after the user presses Ctrl+Break and cancel the termination of the application.

Applies to

See also