Writing a custom formatter for log4net

public class ExceptionLayoutExtended : log4net.Layout.LayoutSkeleton {
   
   private PatternLayout patternLayout;
   PatternLayout PatternLayout {
      get { return patternLayout ?? (patternLayout = new PatternLayout(Pattern)); }
   }
public ExceptionLayoutExtended() {
   this.IgnoresException = false;
}

public String Pattern { get; set; }

 1 override public void Format(TextWriter writer, LoggingEvent loggingEvent) {
 2    if (loggingEvent == null) {
 3       throw new ArgumentNullException("loggingEvent");
 4    }
 5    ;
 6    String header = String.Empty;
 7    writer.Write("n-EXCEPTION EXTENDED LOG START");
 8    //writer.Write("nBASE MESSAGE:" + loggingEvent.MessageObject);
 9    PatternLayout.Format(writer, loggingEvent);
10    Exception curEx = loggingEvent.ExceptionObject;
11  
12    while (curEx != null) {
13       writer.Write(header + "nExceptionMessage:  ");
14       writer.Write(header + curEx.Message);
15       writer.Write(header + "nExceptionType:    ");
16       writer.Write(header + curEx.GetType().FullName);
17 
18       writer.Write(header + "nStackTrace:    ");
19       if (curEx.StackTrace != null) {
20          writer.Write(header + curEx.StackTrace.ToString());
21       }
22       curEx = curEx.InnerException;
23       if (curEx != null) {
24          writer.Write("n" + header + "INNER EXCEPTION");
25          header += new string('-', 4);
26       }
27    }
28    writer.Write("nEXCEPTION EXTENDED LOG END");
29 
30 }

<appender name="ExceptionAppender" type="log4net.Appender.FileAppender">
   <param name="File" value="Exceptions.txt" />
   <param name="AppendToFile" value="true" />
   <layout type="mynamespace.ExceptionLayoutExtended, MyAssembly" >
      <param name="Pattern" value="%d - %exception% Detail:%m%newline" />
   </layout>
</appender>