Where does System.Diagnostics.Debug.Write output appear?

Question

The following C# program (built with csc hello.cs) prints just Hello via Console! on the console and Hello via OutputDebugString in the DebugView window. However, I cannot see either of the System.Diagnostics.* calls. Why is that?

using System;
using System.Runtime.InteropServices;
class Hello {
    [DllImport("kernel32.dll", CharSet=CharSet.Auto)]
    public static extern void OutputDebugString(string message);

    static void Main() {
        Console.Write( "Hello via Console!" );
        System.Diagnostics.Debug.Write( "Hello via Debug!" );
        System.Diagnostics.Trace.Write( "Hello via Trace!" );
        OutputDebugString( "Hello via OutputDebugString" );
    }
}

Is there maybe some special command-line switches required for csc?

I'm not using Visual Studio for any of my development, this is pure commandline stuff.

as mentioned at some comment in another reply, can use Microsoft's (SysInternals) DebugView: http://technet.microsoft.com/en-us/sysinternals/bb896647.aspx — George Birbilis, Sep 26 '14 at 15:10

score 125 · Answer 1 · edited Apr 16 '17 at 14:31

125

While debugging System.Diagnostics.Debug.WriteLine will display in the output window (Ctrl+Alt+O), you can also add a TraceListener to the Debug.Listeners collection to specify Debug.WriteLine calls to output in other locations.

Note: Debug.WriteLine calls may not display in the output window if you have the Visual Studio option "Redirect all Output Window text to the Immediate Window" checked under the menu Tools → Options → Debugging → General. To display "Tools → Options → Debugging", check the box next to "Tools → Options → Show All Settings".

edited Apr 16 '17 at 14:31

Peter Mortensen

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answered Jul 21 '09 at 15:15

boardernin

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I would like to confirm that (Ctrl + Alt + O) will bring up the output window while debugging in Visual Studio 2012 – Ishikawa Aug 26 '12 at 18:54

Tormod Fjeldskår · Accepted Answer · 2009-07-21T15:26:47.980

82

As others have pointed out, listeners have to be registered in order to read these streams. Also note that Debug.Write will only function if the DEBUG build flag is set, while Trace.Write will only function if the TRACE build flag is set.

Setting the DEBUG and/or TRACE flags is easily done in the project properties in Visual Studio or by supplying the following arguments to csc.exe

/define:DEBUG;TRACE

edited Jul 21 '09 at 15:26

answered Jul 21 '09 at 15:10

Tormod Fjeldskår

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It was useful (didn't expect that) for me to find out that Debug and Trace objects use the same trace listeners, therefore, both Debug.Write and Trace.Write output to the same place(s), it is just that depending on conditions they might not get executed – hello_earth Feb 14 '11 at 16:54
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could you elaborate on what *conditions* they are? exactly which situation a debug.Write will not work the same as a trace.write? – Pacerier Jul 29 '11 at 16:41
2

this doesnt work for me, i have debug and trace flags set in vs project properties, and am using Debug.WriteLine, the line executes, but nothing appears in the output window, anyone got any other advise? – f1wade Dec 16 '14 at 13:12
To expand on @hello_earth comment, see https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.debug.write?view=net-5.0 – Kevin S. Miller Feb 16 '21 at 19:34

score 50 · Answer 3 · answered Jul 21 '09 at 15:03

50

You need to add a TraceListener to see them appear on the Console.

TextWriterTraceListener writer = new TextWriterTraceListener(System.Console.Out);
Debug.Listeners.Add(writer);

They also appear in the Visual Studio Output window when in Debug mode.

answered Jul 21 '09 at 15:03

jason

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Apparently DebugView will capture both the .NET Debug.Write() and Win32 OutputDebugString(): http://technet.microsoft.com/en-us/sysinternals/bb896647 – dlchambers Dec 15 '11 at 17:29
@dlchambers: I don't think that's correct. That page claims display of `OutputDebugString()` and (kernel) `DbgPrint().` – Mike C Jan 22 '15 at 00:50
1

@dlchambers: I withdraw the comment; I discovered that DebugView can capture `Debug.Write()` *if* its Capture settings include "Global Win32" -- which requires running it in Admin mode. – Mike C Jan 22 '15 at 01:34

score 13 · Answer 4 · answered Jul 21 '09 at 15:03

13

While you are debugging in Visual Studio, display the "Output" window (View->Output). It will show there.

answered Jul 21 '09 at 15:03

Pat

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score 7 · Answer 5 · edited Mar 11 '20 at 18:57

7

The Diagnostics messages are displayed in the Output Window.

edited Mar 11 '20 at 18:57

TylerH

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answered Jul 21 '09 at 15:03

Andreas Grech

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score 5 · Answer 6 · edited Apr 16 '17 at 14:33

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When I write debug.write("") in the code, it outputs in the "Immediate window", not "Output window".

You can try it. For displaying the "Immediate" window (Debug → Window → Immediate).

edited Apr 16 '17 at 14:33

Peter Mortensen

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answered Jan 14 '15 at 12:21

kykbr

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score 2 · Answer 7 · answered Dec 15 '16 at 22:21

2

The solution for my case is:

Right click the output window;
Check the 'Program Output'

answered Dec 15 '16 at 22:21

Ning Zhu

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score 1 · Answer 8 · edited Apr 16 '17 at 14:35

For VB.NET the following applies. You have to select "Debug" AND make sure that you "Start Debugging". This can be reached by pressing F5.

Also the Console.WriteLine will only display messages when building as "Release" in your Output window.

As mentioned before, open the Output window with View → Output AND make sure to select either "Build" if you want to see Console.WriteLine messages or "Debug" if you want to see Debug.WriteLine or Trace.WriteLine messages.

Where does System.Diagnostics.Debug.Write output appear?

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