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I've got a method with some overloads to handle logging, and am noticing some (to me) bizarre behavior. The overloads (which are in a class that my other classes inherit) generate a stacktrace and call the main logging method that then writes out a line which ostensibly includes the calling class and method:

class Global
{
    public static void LogLine(string logline, StackTrace st)
    {
        string cmethod = st.GetFrame(1).GetMethod().Name;
        string cclass = st.GetFrame(1).GetMethod().DeclaringType.Name;
        string logsuffix = String.Format(" ({0}.{1})", cclass, cmethod);
        string curDir = Directory.GetCurrentDirectory();
        string logfile = String.Format(@"{0}\logs\Logfile_{1}.log", curDir, DateTime.Today.ToString("yyyyMMdd"));
        using (System.IO.StreamWriter log = new System.IO.StreamWriter(logfile, true))
        {
            string curtime = String.Format("[{0}]: ", DateTime.Now.ToString("yyyyMMdd-HHmm"));
            log.WriteLine(curtime + logline + logsuffix);
        }
        return;
    }

    public static void WLog(string logline)
    {
        StackTrace st = new StackTrace();
        LogLine(logline, st);
    }

    public static void WLog(string logline, object obj0)
    {
        StackTrace st = new StackTrace();
        LogLine(string.Format(logline, obj0), st);
    }
}

Now the bizarre behavior. This will generate a nullreference exception:

class Program : Global
    {
        static void Main(string[] args)
        {
            string text = "rando text";
            WLog(text);
        }
    }

If I wrap the string in string.Format in WLog(string), it works just fine:

   public static void WLog(string logline)
    {
        StackTrace st = new StackTrace();
        LogLine(string.Format(logline), st);
    }

Can anyone help me understand why this is happening?

The generated exception:

Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object.
   at ...Global.LogLine(String logline, StackTrace st) in ...\Global.cs:line 15
   at ...Program.Main(String[] args) in ...\Program.cs:line 24
JohnnyPrimus
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  • 2
  • Where is the `NullReferenceException` coming from? Put a `try-catch` in the `WLog()` method and see if the string being passed is null or if it's happening within the method. – Barry O'Kane Jun 10 '16 at 15:13
  • I suppose you've already checked the following post : [What is a NullReferenceException and How do I fix It ?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it). Also telling us which line throws the exception would help us to identify the problem – Sidewinder94 Jun 10 '16 at 15:14
  • I've read the link you posted and didn't find anything that could help me with this string behavior. The exception is thrown at LogLine, will edit the post with the exception. Also, I edited the post to more accurately describe the behavior and solution. Wrapping the call to WLog from Program.Main doesn't actually fix. To fix I need to wrap the call from WLog to LogLine in string.Format.... – JohnnyPrimus Jun 10 '16 at 15:28

0 Answers0