Console in windows forms application

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Console in windows forms application

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#1 by (4 votes)

3

I have a class where you open the console, show some data and then close, when executing a second time (without closing the program), an exception occurs in Console.WriteLine("")

If run once, everything works
If you close and open the program again, everything works.
If you try to run the ExportarArquivos() routine twice, without closing the application before the following error occurs:

Error: Invalid handle.

StackTrace:em System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
 em System.IO.__ConsoleStream.Write(Byte[] buffer, Int32 offset, Int32 count)
em System.IO.StreamWriter.Flush(Boolean flushStream, Boolean flushEncoder)
em System.IO.StreamWriter.Write(Char[] buffer, Int32 index, Int32 count)
em System.IO.TextWriter.WriteLine(String value)
em System.IO.TextWriter.SyncTextWriter.WriteLine(String value)
em System.Console.WriteLine(String value)'

Class:

public static class Exportar
{
    [DllImport("kernel32.dll")]
    static extern bool AllocConsole();

    [DllImport("kernel32.dll")]
    static extern bool FreeConsole();


    public static void ExportarArquivos()
    {
        bool aux = AllocConsole();
        Console.WriteLine(""); //ocorre a exceção aqui (na segunda vez), e aux == true neste ponto.
        Console.WriteLine("Gerando arquivos...");

        //Trabalha um pouco

        Console.WriteLine("");
        Console.WriteLine("Pressione qualquer tecla para sair");

        Console.ReadKey();
        FreeConsole();

    }

}

Does anyone know what might be causing this?

c# winforms

asked by anonymous 24.11.2016 / 20:31

1 answer

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score 4 · Accepted Answer

It must be because you are declaring a variable with AllocConsole() twice, creating a condition to avoid this. First, declare a Boolean tester (as a global variable, not within the method):

private bool isConsoleVisible = false;

and then handle this condition:

public static void ExportarArquivos()
{
    if (isConsoleVisible == false) {
         AllocConsole(); // não precisa criar uma variável para isso
         isConsoleVisible = true;
    } else {
         //FreeConsole(); // se quiser que ele se oculte, "descomente" isso
         //isConsoleVisible = false; // e isso também
    }

    Console.WriteLine(""); //ocorre a exceção aqui (na segunda vez), e aux == true neste ponto.
    Console.WriteLine("Gerando arquivos...");

    //Trabalha um pouco

    Console.WriteLine("");
    Console.WriteLine("Pressione qualquer tecla para sair");

    Console.ReadKey();

    if (isConsoleVisible) FreeConsole; // se estiver visível, desapareça 

}

[EDIT]

It worked this way, with a hint removed from here .

[DllImport("user32.dll")]
static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

const int SW_HIDE = 0;
const int SW_SHOW = 5;

public static void ExportarArquivos()
{
    if (isConsoleVisible == false)
    {
        AllocConsole(); 
        isConsoleVisible = true;
    }
    else
    {
        Console.Clear();
        ShowWindow(GetConsoleWindow(), SW_SHOW);
    }

    //Trabalha um pouco

    Console.WriteLine("");
    Console.WriteLine("Pressione qualquer tecla para sair");

    Console.ReadKey();

    ShowWindow(GetConsoleWindow(), SW_HIDE);

}