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: technet.microsoft.com/en-us/sysinternals/bb896647.aspx — George Birbilis
– George Birbilis, Commented Sep 26, 2014 at 15:10

Peter Mortensen · Accepted Answer · 2017-04-16 14:31:55Z

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".

I would like to confirm that (Ctrl + Alt + O) will bring up the output window while debugging in Visual Studio 2012

Tormod Fjeldskår · Accepted Answer · 2009-07-21 15:26:47Z

83

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, 2009 at 15:26

answered Jul 21, 2009 at 15:10

Tormod Fjeldskår

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4 Comments

hello_earth Over a year ago

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

Pacerier Over a year ago

could you elaborate on what conditions they are? exactly which situation a debug.Write will not work the same as a trace.write?

f1wade Over a year ago

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?

Kevin S. Miller Over a year ago

To expand on @hello_earth comment, see learn.microsoft.com/en-us/dotnet/api/…

jason · Accepted Answer · 2009-07-21 15:03:40Z

52

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, 2009 at 15:03

jason

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3 Comments

dlchambers Over a year ago

Apparently DebugView will capture both the .NET Debug.Write() and Win32 OutputDebugString(): technet.microsoft.com/en-us/sysinternals/bb896647

Mike C Over a year ago

@dlchambers: I don't think that's correct. That page claims display of OutputDebugString() and (kernel) DbgPrint().

Mike C Over a year ago

@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.

Pat · Accepted Answer · 2009-07-21 15:03:16Z

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

TylerH · Accepted Answer · 2020-03-11 18:57:27Z

7

The Diagnostics messages are displayed in the Output Window.

edited Mar 11, 2020 at 18:57

TylerH

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answered Jul 21, 2009 at 15:03

Andreas Grech

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Comments

Mustafa Özçetin · Accepted Answer · 2024-02-23 04:13:40Z

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).

Ning Zhu · Accepted Answer · 2016-12-15 22:21:32Z

The solution for my case is:

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

Peter Mortensen · Accepted Answer · 2017-04-16 14:35:21Z

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.

This helps with VB.NET. Make sure you are Debugging and use System.Diagnostics.Debug.WriteLine("Test"). You'll see the Output in the Debug tab.

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