Console.ReadKey() produces Exception

Question

I have created a Windows Forms Application. In special situations, I open a Console-Window with

    public static void CreateConsole() {
        AllocConsole();
    }


    [DllImport("kernel32")]
    private static extern bool AllocConsole();

When I after call Console.ReadKey() i get an InvalidOperationException:

Cannot read keys when either application does not have a console or when console input has been redirected from a file. Try Console.Read.

When I use Console.Read() it will not work. No keystroke is recognized.

Can someone help me, whats the problem here? Thank you.

Please edit to place the full code example IN your question of what you have tried so we may best assist you. https://learn.microsoft.com/en-us/dotnet/api/system.console.readkey?view=net-5.0 and https://learn.microsoft.com/en-us/dotnet/api/system.console.read?view=net-5.0 for example of use — Mark Schultheiss, May 21 '21 at 16:41
Instead of doing the dllImport stuff try going into the project properties and under application change the output type to console application. That seems to work for me. — cc959, May 21 '21 at 16:42
@CatCraft959 That allows you to optionally show the console window? — ProgrammingLlama, May 21 '21 at 16:43
@Llama No it just shows it all the time but is is relatively easy to hide then: https://stackoverflow.com/questions/3571627/show-hide-the-console-window-of-a-c-sharp-console-application — cc959, May 21 '21 at 16:45

score 0 · Accepted Answer · answered Jun 10 '21 at 23:38

As you might see, your output goes to Visual Studio console, not opened one. To fix that issue you need to reopen console output stream:

if (AllocConsole())
{
    var outHandle = CreateFile("CONOUT$", 
        (uint)(FileConsts.FILE_GENERIC_WRITE | FileConsts.FILE_GENERIC_READ), 
        (uint)(FileConsts.FILE_SHARE_WRITE | FileConsts.FILE_SHARE_READ), 
        0,
        FileConsts.OPEN_EXISTING,
        FileConsts.FILE_ATTRIBUTE_NORMAL, 0);
   
    var inHandle = CreateFile("CONIN$",
        (uint)(FileConsts.FILE_GENERIC_WRITE | FileConsts.FILE_GENERIC_READ),
        (uint)(FileConsts.FILE_SHARE_WRITE | FileConsts.FILE_SHARE_READ),
        0,
        FileConsts.OPEN_EXISTING,
        FileConsts.FILE_ATTRIBUTE_NORMAL, 0);

    if (!SetStdHandle(STD_OUTPUT_HANDLE, outHandle))
        throw new Exception("Can't set std handle");

    if (!SetStdHandle(STD_INPUT_HANDLE, inHandle))
        throw new Exception("Can't set std handle");

    //Just for handle .Dispose();
    var fileStream = new FileStream(new SafeFileHandle(outHandle, true), FileAccess.Write);
    var fileStreamRead = new FileStream(new SafeFileHandle(inHandle, true), FileAccess.Read);

    ConsoleKey read;
    while ((read = Console.ReadKey().Key) != ConsoleKey.Escape)
    {
        Console.WriteLine($"Printed {read}");
    }

    Console.WriteLine("Escape Pressed, exiting");

    SetStdHandle(STD_INPUT_HANDLE, IntPtr.Zero);
    SetStdHandle(STD_OUTPUT_HANDLE, IntPtr.Zero);
    fileStream.Dispose();
    fileStreamRead.Dispose();
    FreeConsole();
}

Note, that new FileStream("CONOUT$", ...) and Console.OpenStandardInput() won't work. I've just tested it with Windows.Forms application. Console.ReadKey works correctly for me. Create file and constants is from kernel32.dll

Console.ReadKey() produces Exception

1 Answers1