System.Diagnostics.TraceSource doesn't read configuration from App.config in .NET Core?

[jemiller0]

The following code outputs "Hello, world!" as a trace message to the console when in a .NET Framework console application. When the same code is used in a .NET Core console application, it outputs nothing.

Program.cs

using System.Diagnostics;

namespace ConsoleApp5
{
    class Program
    {
        private readonly static TraceSource traceSource = new TraceSource("ConsoleApp5", SourceLevels.All);

        static void Main(string[] args)
        {
            traceSource.TraceEvent(TraceEventType.Information, 0, "Hello, world!");
        }
    }
}

App.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.diagnostics>
    <trace autoflush="true">
      <listeners>
        <add name="consoleTraceListener" />
        <add name="textWriterTraceListener" />
      </listeners>
    </trace>
    <sharedListeners>
      <add name="consoleTraceListener" type="System.Diagnostics.ConsoleTraceListener" traceOutputOptions="DateTime,ThreadId" />
      <add name="textWriterTraceListener" type="System.Diagnostics.TextWriterTraceListener" traceOutputOptions="DateTime,ThreadId" initializeData="Trace.log" />
    </sharedListeners>
    <sources>
      <source name="ConsoleApp5" switchValue="Verbose">
        <listeners>
          <add name="consoleTraceListener" />
          <add name="textWriterTraceListener" />
        </listeners>
      </source>
    </sources>
  </system.diagnostics>
</configuration>

Also, I found that if I try to read a connection string using System.Configuration.ConfigurationManager and I have the system.diagnostics section in the App.config, I receive the following error. I'm assuming that .NET Core doesn't have a machine.config where the system.diagnostics section would normally be defined?

Unhandled Exception: System.Configuration.ConfigurationErrorsException: Configuration system failed to initialize ---> System.Configuration.ConfigurationErrorsException: Unrecognized configuration section system.diagnostics. (C:\Users\jemiller\Documents\Visual Studio 2017\Projects\Library2\LibraryConsoleApplication\bin\Debug\netcoreapp2.0\LibraryConsoleApplication.dll.config line 6)
   at System.Configuration.ConfigurationSchemaErrors.ThrowIfErrors(Boolean ignoreLocal)
   at System.Configuration.BaseConfigurationRecord.ThrowIfParseErrors(ConfigurationSchemaErrors schemaErrors)
   at System.Configuration.ClientConfigurationSystem.EnsureInit(String configKey)
   --- End of inner exception stack trace ---
   at System.Configuration.ClientConfigurationSystem.EnsureInit(String configKey)
   at System.Configuration.ClientConfigurationSystem.PrepareClientConfigSystem(String sectionName)
   at System.Configuration.ClientConfigurationSystem.System.Configuration.Internal.IInternalConfigSystem.GetSection(String sectionName)
   at System.Configuration.ConfigurationManager.GetSection(String sectionName)
   at System.Configuration.ConfigurationManager.get_ConnectionStrings()
   at LibraryLibrary.LibraryContext..ctor(String name) in C:\Users\jemiller\Documents\Visual Studio 2017\Projects\Library2\LibraryLibrary\LibraryContext.cs:line 43
   at LibraryLibrary.LibraryContext..ctor() in C:\Users\jemiller\Documents\Visual Studio 2017\Projects\Library2\LibraryLibrary\LibraryContext.cs:line 39
   at LibraryConsoleApplication.Program.Main(String[] args) in C:\Users\jemiller\Documents\Visual Studio 2017\Projects\Library2\LibraryConsoleApplication\Program.cs:line 13

Is there I way I could specify the section similar to the following to get it to work? That is how it is defined in machine.config for .NET Framework.

  <configSections>
    <section name="system.diagnostics" type="System.Diagnostics.SystemDiagnosticsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>
  </configSections>

Is there some other way in .NET Core to specify that configuration settings for system.diagnostics?

[jemiller0]

I looked at the source code for TraceSource in .NET Core. It appears that the code does not read configuration settings from App.config. In addition, it looks like .NET Core doesn't even have a ConsoleTraceListener. So, it looks like you can't even log to the console using TraceSource even if you programmatically configured it.

[danmoseley]

@brianrob could you please answer the questions above about trace source?

When TraceSource was written, we did not have configuration API's. Now we do, and TraceSource could presumably be changed to read app.config, but @brianrob note this would presumably mean pulling System.Configuration.ConfigurationManager library into the shared framework, as it is not currently in it.

[jemiller0]

I can't even get it to work by programmatically adding a TextWriterTraceListener. The following code works with .NET Framework, but, does nothing with .NET Core.

using System.Diagnostics;

namespace ConsoleApp5
{
    class Program
    {
        private readonly static TraceSource traceSource = new TraceSource("ConsoleApp5", SourceLevels.All);

        static void Main(string[] args)
        {
            Trace.AutoFlush = true;
            traceSource.Listeners.Add(new TextWriterTraceListener("Trace.log"));
            traceSource.TraceEvent(TraceEventType.Information, 0, "Hello, world!");
        }
    }
}

As far as I can tell, TraceSource is just flat out broken and unusable in .NET Core.

[danmoseley]

OK, @brianrob or @vancem need to give guidance...

[jemiller0]

So, why is this being closed? TraceSource is basically completely non-usable as it stands now.

[danmoseley]

Because the Close button is too close to the Comment button :)

[MikeDempseyFL]

I'm no expert on tracing but I am currently trying to figure out how to turn on network tracing for sockets - replacing the app.config entries for system.diagnostics with whatever is required to have the same effect in .NET Core.

While looking into this I found that TextWriterTraceListener did not seem to work as expected, but by using DefaultTraceListner I could write the output I expected.

In your example you would simply replace:
traceSource.Listeners.Add(new TextWriterTraceListener("Trace.log"));
with:
traceSource.Listeners.Add(new DefaultTraceListener());
DefaultTraceListener dtl = (DefaultTraceListener) traceSource.Listeners["Default"];
dtl.LogFileName ="Trace.log";

To avoid writing to the debug output window twice add the following before this code:
traceSource.Listeners.Clear();

My guess is that this is not really what you want to do - you are just playing around with a very simplified version of tracing as a means of trying to figure out how this works in Core. If anyone can describe how to configure network tracing in Core I'm sure there would be a lot of folks interested.

[jemiller0]

Do you know if that applies to all instances of TraceSource? If yes, then, maybe it would be possible to use. Otherwise, you need the configuration file because chances are you have many instances of TraceSource and configuring them programmatically isn't feasible.

[MikeDempseyFL]

In my own test I simply used
Trace.Listeners.Add()
rather than creating my own source so the issue is generic from that point of view.

[wilson0x4d]

@danmosemsft @brianrob probably this is asked a million times for a million things, but, any idea when this bug might get picked up? It's a pretty powerful and often undervalued facility that is mostly useless from an operational standpoint because "configuration management" means changing code and redeploying (or we continue sticking to .NET Framework for these features.)

[jemiller0]

ConfigurationManager is there now. However, it has been lobotomized and only supports things like ConnectionStrings. And App.config doesn't work in certain contexts, like if you have a unit test assembly, it is not read. System.Diagnostics.TraceSource doesn't use App.config in .NET Core. So, you have to programmatically configure every single instance you have, making it for practical purposes unusable.

[danmoseley]

@JeremyKuhne also

[brianrob]

From #16332: In general, we are not expanding support for TraceSource. However, if there is someone who is interested in contributing support for System.Configuration, I think that is OK.

I am marking this up-for-grabs. Next step is to propose a design.