Logger.cs

public static class Logger
{
	private const uint HRFileLocked = 0x80070020;
	private const uint HRPortionOfFileLocked = 0x80070021;
	
	[ThreadStatic]
	private static bool IsRecursive;

	public static void Initialise()
	{
		//Subscribe for domain exception diring initialization.
		AppDomain.CurrentDomain.FirstChanceException += OnCurrentDomainOnFirstChanceException;
	}

	private static void OnCurrentDomainOnFirstChanceException(object o, FirstChanceExceptionEventArgs args)
	{
		if (exception is IOException)
		{
			return; // can`t write something to file, so do nothing to prevent stack overflow
		}

		if (IsRecursive)
			return;

		try
		{
			IsRecursive = true;
			Logger.LogException(exception);
		}
		catch
		{
			// prevent stack overflow
		}
		finally
		{
			IsRecursive = false;
		}
	}

	private static void LogException(Exception exception)
	{
		String path = Path.Combine(AppDomain.CurrentDomain.GetData("DataDirectory").ToString(), "MyLog.log");

		var trace = new StackTrace(2);
		//Check your exception here
		if (IsExcluded(exception, trace))
			return;

		Stream stream;
		while (!TryOpen(path, out stream))
		{
			Thread.Sleep(100); // wait for file to unlock
		}
		using (stream)
		{
			//Write your log here
			StreamWriter tw = new StreamWriter(stream);
			tw.WriteLine("\n================================================================================");
			tw.Write(DateTime.Now.ToString("MMM/dd HH:mm:ss.ffff  "));

			tw.WriteLine();
			tw.WriteLine("Message: " + exception.Message);
			tw.WriteLine();

			tw.Close();
		}
	}


	private static bool IsExcluded(Exception exception, StackTrace trace)
	{
		return !exception.Message.Contains("Session has expired");
	}
	private static bool FileIsLocked(IOException ioException)
	{
		var errorCode = (uint)Marshal.GetHRForException(ioException);
		return errorCode == HRFileLocked || errorCode == HRPortionOfFileLocked;
	}
	private static bool TryOpen(string path, out Stream stream)
	{
		try
		{
			stream = File.Open(path, FileMode.Append);
			return true;
		}
		catch (IOException e)
		{
			if (!FileIsLocked(e))
				throw;

			stream = null;
			return false;
		}
	}
}