TraceSource and ASP.NET: Works for Web Applications, not WebSites

Question

I'm adding tracing functionality to an ASP.NET website so I decided to investigate TraceSource by creating a couple of prototypes; a Web Application project and a Website project.

I'm using similar Web.config for each project to log traces to the Windows Event Log:

<configuration>
    <system.web>
        <compilation debug="true" strict="false" explicit="true" targetFramework="4.0"/>
    </system.web>    
    <system.diagnostics>
        <trace autoflush="true" />
        <sources>
            <source name="HelloWorld">
                <listeners>
                    <add name="eventlogListener" />
                </listeners>
            </source>
        </sources>    
        <sharedListeners>
            <add name="eventlogListener" type="System.Diagnostics.EventLogTraceListener" initializeData="My Source" />
        </sharedListeners>
    </system.diagnostics>
</configuration>

I'm simply starting with the following basic trace:

private static TraceSource _ts = new TraceSource("HelloWorld", SourceLevels.All);

protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);

    _ts.TraceEvent(TraceEventType.Information, 10, "Greetings from OnLoad.");
}

With the Web Application project, I can see the trace created in the Event Log. However, with the Website project, I cannot.

Are additional steps (Ex: web.config settings, permissions, etc) required with the Website projects to use TraceSource?

Answer 1

After some trial and error, apparently the system.codedom\compilers node is required in the web.config, but I'm not entirely sure why.

Answer 2

The reason for this is because the Trace methods are only compiled by .Net if the TRACE constant is defined as part of the compile. In a Web Site project, the way to do this is to include compiler configuration in your web.config file, like this:

  <system.codedom>
    <compilers>
      <compiler
         language="c#;cs;csharp"
         extension=".cs"
         type="Microsoft.CSharp.CSharpCodeProvider, System, Version=2.0.50727.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
         compilerOptions="/d:TRACE"
         warningLevel="1" />
    </compilers>
  </system.codedom>

Note the "/d:TRACE" compiler option, which enables the TRACE constant when compiling your code (C# in this example).