Listen for key press in NET console app

Question

How can I continue to run my console application until a key press  like Esc is pressed    I m assuming its wrapped around a while loop  I don t like ReadKey as it blocks operation and asks for a key  rather than just continue and listen for the key press    How can this be done

User · Answer

You can change your approach slightly - use Console.ReadKey() to stop your app, but do your work in a background thread:

static void Main(string[] args)
{
    var myWorker = new MyWorker();
    myWorker.DoStuff();
    Console.WriteLine("Press any key to stop...");
    Console.ReadKey();
}

In the myWorker.DoStuff() function you would then invoke another function on a background thread (using Action<>() or Func<>() is an easy way to do it), then immediately return.

User · Answer

Addressing cases that some of the other answers don t handle well    Responsive  direct execution of keypress handling code  avoids the vagaries of  polling or blocking delays Optionality  global keypress is opt-in  otherwise the app should exit normally Separation of concerns   less invasive listening code  operates independently of normal console app code      Many of the solutions on this page involve polling Console KeyAvailable or blocking on Console ReadKey  While it s true that the  NET Console is not very cooperative here  you can use Task Run to move towards a more modern Async mode of listening    The main issue to be aware of is that  by default  your console thread isn t set up for Async operation--meaning that  when you fall out of the bottom of your main function  instead of awaiting Async completions  your AppDoman and process will end  A proper way to address this would be to use Stephen Cleary s AsyncContext to establish full Async support in your single-threaded console program  But for simpler cases  like waiting for a keypress  installing a full trampoline may be overkill   The example below would be for a console program used in some kind of iterative batch file  In this case  when the program is done with its work  normally it should exit without requiring a keypress  and then we allow an optional key press to prevent the app from exiting  We can pause the cycle to examine things  possibly resuming  or use the pause as a known  control point  at which to cleanly break out of the batch file   static void Main String   args        Console WriteLine  Press any key to prevent exit           var tHold   Task Run      gt  Console ReadKey true                do your console app activity          if  tHold IsCompleted         if false      For the  hold  state  you can simply halt forever            Console WriteLine  Holding             Thread Sleep Timeout Infinite    else                                  or allow continuing to exit         while  Console KeyAvailable              Console ReadKey true          flush consume any extras         Console WriteLine  Holding  Press  Esc  to exit             while  Console ReadKey true  Key    ConsoleKey Escape                 endif

User · Answer

with below code you can listen SpaceBar pressing   in middle of your console execution  and pause until another key is pressed and also listen for EscapeKey for breaking the main loop  static ConsoleKeyInfo cki   new ConsoleKeyInfo      while true          if  WaitOrBreak    break          your main code     private static bool WaitOrBreak            if  Console KeyAvailable  cki   Console ReadKey true           if  cki Key    ConsoleKey Spacebar                        Console Write  waiting                  while  Console KeyAvailable    false                                Thread Sleep 250  Console Write                                 Console WriteLine                Console ReadKey true               cki   new ConsoleKeyInfo                      if  cki Key    ConsoleKey Escape  return true          return false

User · Answer

Use Console KeyAvailable so that you only call ReadKey when you know it won t block   Console WriteLine  Press ESC to stop    do       while    Console KeyAvailable               Do something               while  Console ReadKey true  Key    ConsoleKey Escape

User · Answer

Here is an approach for you to do something on a different thread and start listening to the key pressed in a different thread  And the Console will stop its processing when your actual process ends or the user terminates the process by pressing Esc key   class SplitAnalyser       public static bool stopProcessor   false      public static bool Terminate   false       static void Main string   args                Console ForegroundColor   ConsoleColor Green          Console WriteLine  Split Analyser starts            Console ForegroundColor   ConsoleColor Red          Console WriteLine  Press Esc to quit                 Thread MainThread   new Thread new ThreadStart startProcess            Thread ConsoleKeyListener   new Thread new ThreadStart ListerKeyBoardEvent            MainThread Name    Processor           ConsoleKeyListener Name    KeyListener           MainThread Start            ConsoleKeyListener Start             while  true                         if  Terminate                                Console WriteLine  Terminating Process                       MainThread Abort                    ConsoleKeyListener Abort                    Thread Sleep 2000                   Thread CurrentThread Abort                    return                             if  stopProcessor                                Console WriteLine  Ending Process                       MainThread Abort                    ConsoleKeyListener Abort                    Thread Sleep 2000                   Thread CurrentThread Abort                    return                                      public static void ListerKeyBoardEvent                 do                       if  Console ReadKey true  Key    ConsoleKey Escape                                Terminate   true                          while  true               public static void startProcess                 int i   0          while  true                        if   stopProcessor  amp  amp   Terminate                                Console ForegroundColor   ConsoleColor White                  Console WriteLine  Processing        i                     Thread Sleep 3000                             if i  10                  stopProcessor   true

User · Answer

The shortest way   Console WriteLine  Press ESC to stop     while    Console KeyAvailable  amp  amp  Console ReadKey true  Key    ConsoleKey Escape            do something     Console ReadKey   is a blocking function  it stops the execution of the program and waits for a key press  but thanks to checking Console KeyAvailable first  the while loop is not blocked  but running until the Esc is pressed

User · Answer

If you are using Visual Studio  then you can use  Start Without Debugging  in the Debug menu   It will automatically write  Press any key to continue        to the console for you upon completion of the application and it will leave the console open for you until a key is pressed

User · Answer

From the video curse Building  NET Console Applications in C  by Jason Roberts at http   www pluralsight com  We could do following to have multiple running process    static void Main string   args                Console CancelKeyPress     sender  e    gt                         Console WriteLine  Exiting                   Environment Exit 0                       Console WriteLine  Press ESC to Exit             var taskKeys   new Task ReadKeys           var taskProcessFiles   new Task ProcessFiles            taskKeys Start            taskProcessFiles Start             var tasks   new     taskKeys            Task WaitAll tasks              private static void ProcessFiles                 var files   Enumerable Range 1  100  Select n   gt   File    n     txt             var taskBusy   new Task BusyIndicator           taskBusy Start             foreach  var file in files                        Thread Sleep 1000               Console WriteLine  Procesing file  0    file                        private static void BusyIndicator                 var busy   new ConsoleBusyIndicator            busy UpdateProgress               private static void ReadKeys                 ConsoleKeyInfo key   new ConsoleKeyInfo             while   Console KeyAvailable  amp  amp  key Key    ConsoleKey Escape                         key   Console ReadKey true                switch  key Key                                case ConsoleKey UpArrow                      Console WriteLine  UpArrow was pressed                        break                  case ConsoleKey DownArrow                      Console WriteLine  DownArrow was pressed                        break                   case ConsoleKey RightArrow                      Console WriteLine  RightArrow was pressed                        break                   case ConsoleKey LeftArrow                      Console WriteLine  LeftArrow was pressed                        break                   case ConsoleKey Escape                      break                   default                      if  Console CapsLock  amp  amp  Console NumberLock                                                Console WriteLine key KeyChar                                             break                                   internal class ConsoleBusyIndicator       int  currentBusySymbol       public char   BusySymbols   get  set         public ConsoleBusyIndicator                 BusySymbols   new                -                     public void UpdateProgress                 while  true                        Thread Sleep 100               var originalX   Console CursorLeft              var originalY   Console CursorTop               Console Write BusySymbols  currentBusySymbol                  currentBusySymbol                 if   currentBusySymbol    BusySymbols Length                                 currentBusySymbol   0                             Console SetCursorPosition originalX  originalY

User · Answer

According to my experience  in console apps the easiest way to read the last key pressed is as follows  Example with arrow keys    ConsoleKey readKey   Console ReadKey    Key  if  readKey    ConsoleKey LeftArrow         lt Method1 gt         Do something   else if  readKey    ConsoleKey RightArrow         lt Method2 gt         Do something     I use to avoid loops  instead I write the code above within a method  and I call it at the end of both  Method1  and  Method2   so  after executing  Method1  or  Method2   Console ReadKey   Key is ready to read the keys again

[c#] Listen for key press in .NET console app

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