Audit Trail with NHibernate Using a Custom log4net Appender

Audit.sql

CREATE TABLE [dbo].[Audit]
(
    [Id] INT NOT NULL IDENTITY,
    [User] NVARCHAR( 100 ) NOT NULL,
    [Trail] NVARCHAR( MAX ) NOT NULL,
    [Created] DATETIME NOT NULL
)

ALTER TABLE [dbo].[Audit]
    ADD CONSTRAINT [PK_Audit_Id]
    PRIMARY KEY (Id)

gistfile1.cs

public class NHibernateAuditAppender : AppenderSkeleton
{
    private static IKernel kernel;

    protected override void Append( LoggingEvent loggingEvent )
    {
#if !DEBUG
        if( loggingEvent.RenderedMessage.StartsWith( "SELECT" ) )
        {
            return;
        }
#endif

        var session = kernel.Get<ISession>();
        var audit = new Audit
        {
            Created = DateTime.UtcNow,
            Trail = loggingEvent.RenderedMessage,
            User = Thread.CurrentPrincipal.Identity.Name
        };
        session.Save( audit );
    }
}

NHibernateAuditAppender.cs

public class NHibernateAuditAppender : AppenderSkeleton
{
    private static IKernel kernel;

    protected override void Append( LoggingEvent loggingEvent )
    {
#if !DEBUG
        if( loggingEvent.RenderedMessage.StartsWith( "SELECT" ) )
        {
            return;
        }
#endif

        var session = kernel.Get<ISession>();
        var audit = new Audit
        {
            Created = DateTime.UtcNow,
            Trail = loggingEvent.RenderedMessage,
            User = Thread.CurrentPrincipal.Identity.Name
        };
        session.Save( audit );
    }

    public static void RegisterAppender( IKernel kernel )
    {
        NHibernateAuditAppender.kernel = kernel;

        var repository = (Hierarchy)LogManager.GetRepository();
        var appender = new NHibernateAuditAppender { Name = "NHibernateAuditAppender" };
        var logger = (Logger)repository.GetLogger( "NHibernate.SQL" );
        logger.Level = Level.Debug;
        logger.Additivity = false;
        logger.AddAppender( appender );
        appender.ActivateOptions();
        repository.Configured = true;
    }
}