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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.?

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1 Answer 1

Reset to default
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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
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2 Comments

Appreciate your response @pfx, may i know what is this line <filter initializeData="All" type="System.Diagnostics.EventTypeFilter"/> 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.
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.

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