Where does Console WriteLine go in ASP NET

Question

In a J2EE application  like one running in WebSphere   when I use System out println    my text goes to standard out  which is mapped to a file by the WebSphere admin console   In an ASP NET application  like one running in IIS   where does the output of Console WriteLine   go   The IIS process must have a stdin  stdout and stderr  but is stdout mapped to the Windows version of  dev null or am I missing a key concept here   I m not asking if I should log there  I use log4net   but where does the output go   My best info came from this discussion where they say Console SetOut   can change the TextWriter  but it still didn t answer the question on what the initial value of the Console is  or how to set it in config outside of runtime code

User · Answer

If you use System Diagnostics Debug WriteLine      instead of Console WriteLine    then you can see the results in the Output window of Visual Studio

User · Answer

System Diagnostics Debug WriteLine       gets it into the Immediate Window in Visual nbsp Studio nbsp 2008   Go to menu Debug -  Windows -  Immediate

User · Answer

if you happened to use NLog in your ASP net project  you can add a Debugger target    lt targets gt       lt target name  debugger  xsi type  Debugger              layout    date format HH  mm  ss    pad padding 5 inner   level uppercase true     message     gt    and writes logs to this target for the levels you want    lt rules gt       lt logger name     minlevel  Trace  writeTo  debugger    gt    now you have console output just like Jetty in  Output  window of VS  and make sure you are running in Debug Mode F5

User · Answer

I ve found this question by trying to change the Log output of the DataContext to the output window  So to anyone else trying to do the same   what I ve done was create this   class DebugTextWriter   System IO TextWriter      public override void Write char   buffer  int index  int count           System Diagnostics Debug Write new String buffer  index  count             public override void Write string value           System Diagnostics Debug Write value            public override Encoding Encoding          get   return System Text Encoding Default             Annd after that  dc Log   new DebugTextWriter   and I can see all the queries in the output window  dc is the DataContext    Have a look at this for more info  http   damieng com blog 2008 07 30 linq-to-sql-log-to-debug-window-file-memory-or-multiple-writers

User · Answer

If you are using IIS Express and launch it via a command prompt  it will leave the DOS window open  and you will see Console Write statements there   So for example get a command window open and type    C  Program Files  x86  IIS Express iisexpress   path C  Projects Website1  port 1655   This assumes you have a website directory at C  Projects Website1  It will start IIS Express and serve the pages in your website directory  It will leave the command windows open  and you will see output information there   Let s say you had a file there  default aspx  with this code in it    lt    Page Language  C     gt   lt html gt   lt body gt       lt form id  form1  runat  server  gt      Hello        lt   for int i   0  i  lt  6  i      gt          lt     Console WriteLine i ToString        gt        lt  form gt   lt  body gt   lt  html gt    Arrange your browser and command windows so you can see them both on the screen  Now type into your browser  http   localhost 1655   You will see Hello  on the webpage  but in the command window you will see something like  Request started   GET  http   localhost 1655  0 1 2 3 4 5 Request ended  http   localhost 1655 default aspx with HTTP status 200 0   I made it simple by having the code in a code block in the markup  but any console statements in your code-behind or anywhere else in your code will show here as well

User · Answer

If you look at the Console class in  NET Reflector  you ll find that if a process doesn t have an associated console  Console Out and Console Error are backed by Stream Null  wrapped inside a TextWriter   which is a dummy implementation of Stream that basically ignores all input  and gives no output  So it is conceptually equivalent to  dev null  but the implementation is more streamlined  there s no actual I O taking place with the null device  Also  apart from calling SetOut  there is no way to configure the default  Update 2020-11-02  As this answer is still gathering votes in 2020  it should probably be noted that under ASP NET Core  there usually is a console attached  You can configure the ASP NET Core IIS Module to redirect all stdout and stderr output to a log file via the stdoutLogEnabled and stdoutLogFile settings   lt system webServer gt     lt aspNetCore processPath  quot dotnet quot                arguments  quot   MyApp dll quot                hostingModel  quot inprocess quot                stdoutLogEnabled  quot true quot                stdoutLogFile  quot   logs stdout quot    gt   lt system webServer gt

User · Answer

The TraceContext object in ASP NET writes to the DefaultTraceListener which outputs to the host process    standard output  Rather than using Console Write    if you use Trace Write  output will go to the standard output of the process   You could use the System Diagnostics Process object to get the ASP NET process for your site and monitor standard output using the OutputDataRecieved event

User · Answer

In an ASP NET application  I think it goes to the Output or Console window which is visible during debugging

User · Answer

Unless you are in a strict console application  I wouldn t use it  because you can t really see it  I would use Trace WriteLine   for debugging-type information that can be turned on and off in production

User · Answer

Mac  In Debug mode there is a tab for the Output

User · Answer

This is confusing for everyone when it comes IISExpress  There is nothing to read console messages  So for example  in the ASPCORE MVC apps it configures using appsettings json which does nothing if you are using IISExpress   For right now you can just add loggerFactory AddDebug LogLevel Debug   in your Configure section and it will at least show you your logs in the Debug Output window   Good news CORE 2 0 this will all be changing  https   github com aspnet Announcements issues 255

User · Answer

There simply is no console listening by default  Running in debug mode there is a console attached  but in a production environment it is as you suspected  the message just doesn t go anywhere because nothing is listening

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