CODEWITHSUNDEEP
c#.netwpfconsole
Rob
Rob

Reputation: 26324

No output to console from a WPF application?

I'm using Console.WriteLine() from a very simple WPF test application, but when I execute the application from the command line, I'm seeing nothing being written to the console. Does anyone know what might be going on here?

I can reproduce it by creating a WPF application in VS 2008, and simply adding Console.WriteLine("text") anywhere where it gets executed. Any ideas?

All I need for right now is something as simple as Console.WriteLine(). I realize I could use log4net or somet other logging solution, but I really don't need that much functionality for this application.

Edit: I should have remembered that Console.WriteLine() is for console applications. Oh well, no stupid questions, right? :-) I'll just use System.Diagnostics.Trace.WriteLine() and DebugView for now.

Upvotes: 176

Views: 194278

Answers (10)

lechup
lechup

Reputation: 3150

Old problem, got stuck with @Bip901 solution that sometimes worked but sometimes not, at last came to this code that works in all cases:

// writing to parent console https://stackoverflow.com/a/73971822
public class WriteToConsoleHelper
{
    const uint parentProcessId = 0x0ffffffff;

    [DllImport("kernel32.dll")]
    static extern bool AttachConsole(uint dwProcessId);

    public static void WriteLineToConsole(string message)
    {
        var currentProcessId = (uint)Environment.ProcessId;
        AttachConsole(parentProcessId);

        var originalConsoleOut = Console.Out;
        var writer = new StreamWriter(Console.OpenStandardOutput())
        {
            AutoFlush = true
        };

        Console.SetOut(writer);
        Console.WriteLine(message);
        Console.SetOut(originalConsoleOut);
        
        writer.Dispose();

        AttachConsole(currentProcessId);
    }
}

Upvotes: 1

Brian
Brian

Reputation: 118865

Right click on the project, "Properties", "Application" tab, change "Output Type" to "Console Application", and then it will also have a console, the WPF Applications still runs as expected (even if the Application output type is switched to "Console Application").

Upvotes: 161

Bip901
Bip901

Reputation: 808

Brian's solution is to always open a console when your WPF application starts. If you want to dynamically enable console output (for example, only when launched with certain commandline arguments) call AttachConsole:

[DllImport("kernel32.dll")]
static extern bool AttachConsole(uint dwProcessId);

const uint ATTACH_PARENT_PROCESS = 0x0ffffffff;

Then, when you want to start writing to the console:

AttachConsole(ATTACH_PARENT_PROCESS);
Console.WriteLine("Hello world!");
Console.WriteLine("Writing to the hosting console!");

Upvotes: 5

Emelias Alvarez
Emelias Alvarez

Reputation: 41

I've create a solution, mixed the information of varius post.

Its a form, that contains a label and one textbox. The console output is redirected to the textbox.

There are too a class called ConsoleView that implements three publics methods: Show(), Close(), and Release(). The last one is for leave open the console and activate the Close button for view results.

The forms is called FrmConsole. Here are the XAML and the c# code.

The use is very simple:

ConsoleView.Show("Title of the Console");

For open the console. Use:

System.Console.WriteLine("The debug message");

For output text to the console.

Use:

ConsoleView.Close();

For Close the console.

ConsoleView.Release();

Leaves open the console and enables the Close button

XAML

<Window x:Class="CustomControls.FrmConsole"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:CustomControls"
    mc:Ignorable="d"
    Height="500" Width="600" WindowStyle="None" ResizeMode="NoResize" WindowStartupLocation="CenterScreen" Topmost="True" Icon="Images/icoConsole.png">
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="40"/>
        <RowDefinition Height="*"/>
        <RowDefinition Height="40"/>
    </Grid.RowDefinitions>
    <Label Grid.Row="0" Name="lblTitulo" HorizontalAlignment="Center" HorizontalContentAlignment="Center" VerticalAlignment="Center" VerticalContentAlignment="Center" FontFamily="Arial" FontSize="14" FontWeight="Bold" Content="Titulo"/>
    <Grid Grid.Row="1">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="10"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="10"/>
        </Grid.ColumnDefinitions>
        <TextBox Grid.Column="1" Name="txtInner" FontFamily="Arial" FontSize="10" ScrollViewer.CanContentScroll="True" VerticalScrollBarVisibility="Visible" HorizontalScrollBarVisibility="Visible" TextWrapping="Wrap"/>
    </Grid>
    <Button Name="btnCerrar" Grid.Row="2" Content="Cerrar" Width="100" Height="30" HorizontalAlignment="Center" HorizontalContentAlignment="Center" VerticalAlignment="Center" VerticalContentAlignment="Center"/>
</Grid>

The code of the Window:

partial class FrmConsole : Window
{
    private class ControlWriter : TextWriter
    {
        private TextBox textbox;
        public ControlWriter(TextBox textbox)
        {
            this.textbox = textbox;
        }

        public override void WriteLine(char value)
        {
            textbox.Dispatcher.Invoke(new Action(() =>
            {
                textbox.AppendText(value.ToString());
                textbox.AppendText(Environment.NewLine);
                textbox.ScrollToEnd();
            }));
        }

        public override void WriteLine(string value)
        {
            textbox.Dispatcher.Invoke(new Action(() =>
            {
                textbox.AppendText(value);
                textbox.AppendText(Environment.NewLine);
                textbox.ScrollToEnd();
            }));
        }

        public override void Write(char value)
        {
            textbox.Dispatcher.Invoke(new Action(() =>
            {
                textbox.AppendText(value.ToString());
                textbox.ScrollToEnd();
            }));
        }

        public override void Write(string value)
        {
            textbox.Dispatcher.Invoke(new Action(() =>
            {
                textbox.AppendText(value);
                textbox.ScrollToEnd();
            }));
        }

        public override Encoding Encoding
        {
            get { return Encoding.UTF8; }

        }
    }

    //DEFINICIONES DE LA CLASE
    #region DEFINICIONES DE LA CLASE

    #endregion


    //CONSTRUCTORES DE LA CLASE
    #region CONSTRUCTORES DE LA CLASE

    public FrmConsole(string titulo)
    {
        InitializeComponent();
        lblTitulo.Content = titulo;
        Clear();
        btnCerrar.Click += new RoutedEventHandler(BtnCerrar_Click);
        Console.SetOut(new ControlWriter(txtInner));
        DesactivarCerrar();
    }

    #endregion


    //PROPIEDADES
    #region PROPIEDADES

    #endregion


    //DELEGADOS
    #region DELEGADOS

    private void BtnCerrar_Click(object sender, RoutedEventArgs e)
    {
        Close();
    }

    #endregion


    //METODOS Y FUNCIONES
    #region METODOS Y FUNCIONES

    public void ActivarCerrar()
    {
        btnCerrar.IsEnabled = true;
    }

    public void Clear()
    {
        txtInner.Clear();
    }

    public void DesactivarCerrar()
    {
        btnCerrar.IsEnabled = false;
    }

    #endregion  
}

the code of ConsoleView class

static public class ConsoleView
{
    //DEFINICIONES DE LA CLASE
    #region DEFINICIONES DE LA CLASE
    static FrmConsole console;
    static Thread StatusThread;
    static bool isActive = false;
    #endregion

    //CONSTRUCTORES DE LA CLASE
    #region CONSTRUCTORES DE LA CLASE

    #endregion

    //PROPIEDADES
    #region PROPIEDADES

    #endregion

    //DELEGADOS
    #region DELEGADOS

    #endregion

    //METODOS Y FUNCIONES
    #region METODOS Y FUNCIONES

    public static void Show(string label)
    {
        if (isActive)
        {
            return;
        }

        isActive = true;
        //create the thread with its ThreadStart method
        StatusThread = new Thread(() =>
        {
            try
            {
                console = new FrmConsole(label);
                console.ShowDialog();
                //this call is needed so the thread remains open until the dispatcher is closed
                Dispatcher.Run();
            }
            catch (Exception)
            {
            }
        });

        //run the thread in STA mode to make it work correctly
        StatusThread.SetApartmentState(ApartmentState.STA);
        StatusThread.Priority = ThreadPriority.Normal;
        StatusThread.Start();

    }

    public static void Close()
    {
        isActive = false;
        if (console != null)
        {
            //need to use the dispatcher to call the Close method, because the window is created in another thread, and this method is called by the main thread
            console.Dispatcher.InvokeShutdown();
            console = null;
            StatusThread = null;
        }

        console = null;
    }

    public static void Release()
    {
        isActive = false;
        if (console != null)
        {
            console.Dispatcher.Invoke(console.ActivarCerrar);
        }

    }
    #endregion
}

I hope this result usefull.

Upvotes: 2

Smitty
Smitty

Reputation: 1935

Old post, but I ran into this so if you're trying to output something to Output in a WPF project in Visual Studio, the contemporary method is:

Include this:

using System.Diagnostics;

And then:

Debug.WriteLine("something");

Upvotes: 32

Ilya Serbis
Ilya Serbis

Reputation: 22273

It's possible to see output intended for console by using command line redirection.

For example:

C:\src\bin\Debug\Example.exe > output.txt

will write all the content to output.txt file.

Upvotes: 14

antidemon
antidemon

Reputation:

Although John Leidegren keeps shooting down the idea, Brian is correct. I've just got it working in Visual Studio.

To be clear a WPF application does not create a Console window by default.

You have to create a WPF Application and then change the OutputType to "Console Application". When you run the project you will see a console window with your WPF window in front of it.

It doesn't look very pretty, but I found it helpful as I wanted my app to be run from the command line with feedback in there, and then for certain command options I would display the WPF window.

Upvotes: 15

John Leidegren
John Leidegren

Reputation: 60987

You'll have to create a Console window manually before you actually call any Console.Write methods. That will init the Console to work properly without changing the project type (which for WPF application won't work).

Here's a complete source code example, of how a ConsoleManager class might look like, and how it can be used to enable/disable the Console, independently of the project type.

With the following class, you just need to write ConsoleManager.Show() somewhere before any call to Console.Write...

[SuppressUnmanagedCodeSecurity]
public static class ConsoleManager
{
    private const string Kernel32_DllName = "kernel32.dll";

    [DllImport(Kernel32_DllName)]
    private static extern bool AllocConsole();

    [DllImport(Kernel32_DllName)]
    private static extern bool FreeConsole();

    [DllImport(Kernel32_DllName)]
    private static extern IntPtr GetConsoleWindow();

    [DllImport(Kernel32_DllName)]
    private static extern int GetConsoleOutputCP();

    public static bool HasConsole
    {
        get { return GetConsoleWindow() != IntPtr.Zero; }
    }

    /// <summary>
    /// Creates a new console instance if the process is not attached to a console already.
    /// </summary>
    public static void Show()
    {
        //#if DEBUG
        if (!HasConsole)
        {
            AllocConsole();
            InvalidateOutAndError();
        }
        //#endif
    }

    /// <summary>
    /// If the process has a console attached to it, it will be detached and no longer visible. Writing to the System.Console is still possible, but no output will be shown.
    /// </summary>
    public static void Hide()
    {
        //#if DEBUG
        if (HasConsole)
        {
            SetOutAndErrorNull();
            FreeConsole();
        }
        //#endif
    }

    public static void Toggle()
    {
        if (HasConsole)
        {
            Hide();
        }
        else
        {
            Show();
        }
    }

    static void InvalidateOutAndError()
    {
        Type type = typeof(System.Console);

        System.Reflection.FieldInfo _out = type.GetField("_out",
            System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);

        System.Reflection.FieldInfo _error = type.GetField("_error",
            System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);

        System.Reflection.MethodInfo _InitializeStdOutError = type.GetMethod("InitializeStdOutError",
            System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);

        Debug.Assert(_out != null);
        Debug.Assert(_error != null);

        Debug.Assert(_InitializeStdOutError != null);

        _out.SetValue(null, null);
        _error.SetValue(null, null);

        _InitializeStdOutError.Invoke(null, new object[] { true });
    }

    static void SetOutAndErrorNull()
    {
        Console.SetOut(TextWriter.Null);
        Console.SetError(TextWriter.Null);
    }
}

Upvotes: 102

erodewald
erodewald

Reputation: 1825

I use Console.WriteLine() for use in the Output window...

Upvotes: 4

Phobis
Phobis

Reputation: 7754

You can use 

Trace.WriteLine("text");

This will output to the "Output" window in Visual Studio (when debugging).

make sure to have the Diagnostics assembly included:

using System.Diagnostics;

Upvotes: 238

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