Console.KeyAvailable Property

 
System_CAPS_noteNote

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Gets a value indicating whether a key press is available in the input stream.

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

Public Shared ReadOnly Property KeyAvailable As Boolean

Property Value

Type: System.Boolean

true if a key press is available; otherwise, false.

Exception Condition
IOException

An I/O error occurred.

InvalidOperationException

Standard input is redirected to a file instead of the keyboard.

The property value is returned immediately; that is, the KeyAvailable property does not block input until a key press is available.

Use the KeyAvailable property in conjunction with only the ReadKey method, not the Read or ReadLine methods.

The following example demonstrates how to use the KeyAvailable property to create a loop that runs until a key is pressed.

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.
'

.NET Framework
Available since 2.0
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