Trace & Log to file using TraceSource

Question

I'm working on ASP.Net MVC web app, using System.Diagnostics.TraceSource to trace and log to file. Added following to web.config

 <system.diagnostics>    
  <trace autoflush="false" indentsize="4"></trace> // what's this for?  
  <sources>    
    <source name ="WebAppLog">    
      <listeners>    
        <add name="FileLog" type="System.Diagnostics.TextWriterTraceListener" initializeData="PartialView_WebApp.log" traceOutputOptions="DateTime,ThreadId,ProcessId,Timestamp,LogicalOperationStack,Callstack">    
          <filter initializeData="All" type="System.Diagnostics.EventTypeFilter"/>    
        </add>    
        <remove name="Default"/>    
      </listeners>    
    </source>    
  </sources>    
</system.diagnostics>

Added Log.cs to application to log mesages to file.

public class Log  
{  
    static TraceSource source = new TraceSource("WebAppLog"); 
    public static void Message(TraceEventType traceEventType, string message)  
    {  
        short id;  
        switch (traceEventType)  
        {  
            case TraceEventType.Information:  
                id = 3;  
                break;  
            case TraceEventType.Verbose:  
                id = 4;  
                break;  
            default:  
                id = -1;  
                break;  
        }  
        source.TraceEvent(traceEventType, id, message);  
        source.Flush();    
    }
}

Home controller.cs

public ActionResult Index()  
{  
    try  
    {  
        Log.Message(System.Diagnostics.TraceEventType.Information, "Index Action Start");
        // Do work
        Log.Message(System.Diagnostics.TraceEventType.Information, "Index Action End");  
        return View();  
    }  
    catch (Exception ex)  
    {
        throw;  
    }  
}

After executing, i'm able to generate log file but couldn't write anything, always the file size is 0 bytes. What could be the possible mistake.?

pfx · Accepted Answer · 2018-07-17T17:41:14.070

The Switch on a TraceSource determines whether any output gets generated.
By default, if it is not configured, there will be no output.

The value for the Switch matches the log levels that should appear in the output.

It can be set via code:

static TraceSource source = new TraceSource("WebAppLog"); 
source.Switch.Level = SourceLevels.Verbose;

Or via configuration, which is more flexible. Your configuration will look like:

<system.diagnostics>    
     <trace autoflush="false" indentsize="4"></trace> 
     <sources>    
         <source name ="WebAppLog" switchName="mySwitch">    
             <listeners>    
                 <add name="FileLog" type="System.Diagnostics.TextWriterTraceListener" initializeData="c:\tmp\trace.log" traceOutputOptions="DateTime,ThreadId,ProcessId,Timestamp,LogicalOperationStack,Callstack">    
                     <filter initializeData="All" type="System.Diagnostics.EventTypeFilter"/>
                 </add>    
                 <remove name="Default"/>
             </listeners>    
        </source>    
    </sources>    
    <switches>
        <add name="mySwitch" value="Verbose" />
    </switches>
</system.diagnostics>

Regarding your question about

<trace autoflush="false" indentsize="4"></trace>

With autoflush=true you don't have to call source.Flush() explicitly.
The indentsize gets applied in the log output, notice the leading whitespace starting from line 2 in the output fragment below.

WebAppLog Information: 3: Index Action Start
    ProcessId=7416
    LogicalOperationStack=
    ThreadId=1

Appreciate your response @pfx, may i know what is this line `` doing here.?, as per my understanding, the listener `TextWriterTraceListener` filters based on the event type. So if i change to `initializeData="Error"` will this only log Error messages to file.? if so, what is `value="Verbose"` under `switches` doing? Please elaborate this, so that i can understand what's each attribute doing here. — Learn Avid, Jul 19 '18 at 16:15
A `Switch` acts as a filter for a `TraceSource`. A `Filter` acts as a filter for a `Listener`. When using only a single `TraceSource`, I mostly only apply a `Switch`. When it is configured with `value="Error"` then `source.TraceData(TraceEventType.Verbose ...` does not appear in the output. Have a look at this [answer](https://stackoverflow.com/questions/15742595/what-is-the-difference-between-switch-and-filter-in-tracing-in-net). — pfx, Jul 19 '18 at 17:05

Trace & Log to file using TraceSource

1 Answers1