How does System.TraceListener prepend message with process name?
- by btlog
I have been looking at using System.Diagnostics.Trace for doing logging is a very basic app. Generally it does all I need it to do. The downside is that if I call
Trace.TraceInformation("Some info");
The output is "SomeApp.Exe Information: 0: Some info". Initally this entertained me but no longer. I would like to just output "Some info" to console. So I thought writing a cusom TraceListener, rather than using the inbuilt ConsoleTraceListener, would solve the problem. I can see a specific format that I want all the text after the second colon. Here is my attempt to see if this would work.
class LogTraceListener : TraceListener
{
public override void Write(string message)
{
int firstColon = message.IndexOf(":");
int secondColon = message.IndexOf(":", firstColon + 1);
Console.Write(message);
}
public override void WriteLine(string message)
{
int firstColon = message.IndexOf(":");
int secondColon = message.IndexOf(":", firstColon + 1);
Console.WriteLine(message);
}
}
If I output the value of firstColon it is always -1. If I put a break point the message is always just "Some info". Where does all the other information come from?
So I had a look at the call stack at the point just before Console.WriteLine was called. The method that called my WriteLine method is: System.dll!System.Diagnostics.TraceListener.TraceEvent(System.Diagnostics.TraceEventCache eventCache, string source, System.Diagnostics.TraceEventType eventType, int id, string message) + 0x33 bytes
When I use Reflector to look at this message it all seems pretty straight forward. I can't see any code that changes the value of the string after I have sent it to Console.WriteLine. The only method that could posibly change the underlying string value is a call to UnsafeNativeMethods.EventWriteString which has a parameter that is a pointer to the message.
Does anyone understand what is going on here and whether I can change the output to be just my message with out the additional fluff. It seems like evil magic that I can pass a string "Some info" to Console.WriteLine (or any other method for that matter) and the string that output is different.
