Console.KeyAvailable Console.KeyAvailable Console.KeyAvailable Console.KeyAvailable Property

Определение

Возвращает или задает значение, указывающее, доступно ли нажатие клавиши во входном потоке.Gets a value indicating whether a key press is available in the input stream.

public:
 static property bool KeyAvailable { bool get(); };
public static bool KeyAvailable { get; }
member this.KeyAvailable : bool
Public Shared ReadOnly Property KeyAvailable As Boolean

Значение свойства

Значение true, если нажатие клавиши доступно; в противном случае — значение false.true if a key press is available; otherwise, false.

Исключения

Ошибка ввода/вывода.An I/O error occurred.

Стандартный ввод перенаправляется в файл вместо клавиатуры.Standard input is redirected to a file instead of the keyboard.

Примеры

Следующий пример демонстрирует, как использовать KeyAvailable свойства цикл, который выполняется, пока не нажата клавиша.The following example demonstrates how to use the KeyAvailable property to create a loop that runs until a key is pressed.

using namespace System;
using namespace System::Threading;
int main()
{
   ConsoleKeyInfo cki;
   do
   {
      Console::WriteLine( "\nPress a key to display; press the 'x' key to quit." );
      
      // Your code could perform some useful task in the following loop. However, 
      // for the sake of this example we'll merely pause for a quarter second.
      while ( Console::KeyAvailable == false )
            Thread::Sleep( 250 );
      cki = Console::ReadKey( true );
      Console::WriteLine( "You pressed the '{0}' key.", cki.Key );
   }
   while ( cki.Key != ConsoleKey::X );
}

/*
This example produces results similar to the following:

Press a key to display; press the 'x' key to quit.
You pressed the 'H' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'E' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'PageUp' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'DownArrow' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'X' key.
*/
using System;
using System.Threading;

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

       do {
           Console.WriteLine("\nPress a key to display; press the 'x' key to quit.");

           // Your code could perform some useful task in the following loop. However, 
           // for the sake of this example we'll merely pause for a quarter second.
   
           while (Console.KeyAvailable == false)
               Thread.Sleep(250); // Loop until input is entered.
           
           cki = Console.ReadKey(true);
           Console.WriteLine("You pressed the '{0}' key.", cki.Key);
        } while(cki.Key != ConsoleKey.X);
    }
}
/*
This example produces results similar to the following:

Press a key to display; press the 'x' key to quit.
You pressed the 'H' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'E' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'PageUp' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'DownArrow' key.

Press a key to display; press the 'x' key to quit.
You pressed the 'X' key.
*/
Imports System.Threading

Class Sample
   Public Shared Sub Main()
      Dim cki As ConsoleKeyInfo
      
      Do
         Console.WriteLine(vbCrLf & "Press a key to display; press the 'x' key to quit.")

         ' Your code could perform some useful task in the following loop. However, 
         ' for the sake of this example we'll merely pause for a quarter second.
         
         While Console.KeyAvailable = False
            Thread.Sleep(250) ' Loop until input is entered.
         End While
         cki = Console.ReadKey(True)
         Console.WriteLine("You pressed the '{0}' key.", cki.Key)
      Loop While cki.Key <> ConsoleKey.X
   End Sub 
End Class 
'This example produces results similar to the following:
'
'Press a key to display; press the 'x' key to quit.
'You pressed the 'H' key.
'
'Press a key to display; press the 'x' key to quit.
'You pressed the 'E' key.
'
'Press a key to display; press the 'x' key to quit.
'You pressed the 'PageUp' key.
'
'Press a key to display; press the 'x' key to quit.
'You pressed the 'DownArrow' key.
'
'Press a key to display; press the 'x' key to quit.
'You pressed the 'X' key.
'

Комментарии

Значение свойства возвращается немедленно; то есть KeyAvailable свойство не блокирует входных данных, пока не станет доступна клавиши.The property value is returned immediately; that is, the KeyAvailable property does not block input until a key press is available.

Используйте KeyAvailable свойство в сочетании с единственным ReadKey метод, не Read или ReadLine методы.Use the KeyAvailable property in conjunction with only the ReadKey method, not the Read or ReadLine methods.

Применяется к