TxtFileLogger.cs

public interface ILogger
{
    void Write(Exception ex);
    void Write(string logText);
}

public abstract class BaseLogger
    : ILogger
{
    public static string logFilePath = string.Empty;
    public string LogFilePath
    {
        set { logFilePath = value; }
        get { return logFilePath; }
    }

    private static StreamWriter sw = null;

    private static bool WriteLog(string strPathName, Exception objException)
    {
        bool bReturn = false;
        string strException = string.Empty;
        try
        {
            sw = new StreamWriter(strPathName, true);
            sw.WriteLine("Source        : " + objException.Source.ToString().Trim());
            sw.WriteLine("Method        : " + objException.TargetSite.Name.ToString());
            sw.WriteLine("Date          : " + DateTime.Now.ToLongTimeString());
            sw.WriteLine("Time          : " + DateTime.Now.ToShortDateString());
            sw.WriteLine("Computer      : " + Dns.GetHostName().ToString());
            sw.WriteLine("Error         : " + objException.Message.ToString().Trim());
            sw.WriteLine("Stack Trace   : " + objException.StackTrace.ToString().Trim());
            sw.WriteLine("-----------------------------------------------------");
            sw.Flush();
            sw.Close();
            bReturn = true;
        }
        catch (Exception)
        {
            bReturn = false;
        }
        return bReturn;
    }

    private static bool WriteLog(string strPathName, string logText)
    {
        bool bReturn = false;
        string strException = string.Empty;
        try
        {
            sw = new StreamWriter(strPathName, true);
            sw.WriteLine("LogText       : " + logText.Trim());
            sw.WriteLine("Date          : " + DateTime.Now.ToLongTimeString());
            sw.WriteLine("Time          : " + DateTime.Now.ToShortDateString());
            sw.WriteLine("Computer      : " + Dns.GetHostName().ToString());
            sw.WriteLine("-----------------------------------------------------");
            sw.Flush();
            sw.Close();
            bReturn = true;
        }
        catch (Exception)
        {
            bReturn = false;
        }
        return bReturn;
    }

    public static bool ErrorRoutine(Exception objException)
    {
        string strPathName = string.Empty;

        if (logFilePath.Equals(string.Empty))
        {
            //Get Default log file path "LogFile.txt"
            strPathName = GetLogFilePath();
        }
        else
        {
            //If the log file path is not empty but the file
            //is not available it will create it
            if (true != File.Exists(logFilePath))
            {
                if (false == CheckDirectory(logFilePath))
                    return false;

                FileStream fs = new FileStream(logFilePath,
                        FileMode.OpenOrCreate, FileAccess.ReadWrite);
                fs.Close();
            }
            strPathName = logFilePath;
        }
        bool bReturn = true;

        // write the error log to that text file
        if (true != WriteLog(strPathName, objException))
        {
            bReturn = false;
        }
        return bReturn;
    }

    public static bool ErrorRoutine(string logText)
    {
        string strPathName = string.Empty;

        if (logFilePath.Equals(string.Empty))
        {
            strPathName = GetLogFilePath();
        }
        else
        {
            if (true != File.Exists(logFilePath))
            {
                if (false == CheckDirectory(logFilePath))
                    return false;

                FileStream fs = new FileStream(logFilePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
                fs.Close();
            }
            strPathName = logFilePath;
        }
        bool bReturn = true;

        // write the error log to that text file
        if (true != WriteLog(strPathName, logText))
        {
            bReturn = false;
        }
        return bReturn;
    }

    private static string GetLogFilePath()
    {
        try
        {
            string retFilePath = ConfigurationSettings.AppSettings["LogFile"].ToString();
            logFilePath = retFilePath;

            // if exists, return the path
            if (File.Exists(retFilePath) == true)
                return retFilePath;
            //create a text file
            else
            {
                if (false == CheckDirectory(logFilePath))
                    return string.Empty;

                FileStream fs = new FileStream(retFilePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
                fs.Close();
            }

            return retFilePath;
        }
        catch (Exception)
        {
            return string.Empty;
        }
    }

    private static bool CheckDirectory(string strLogPath)
    {
        try
        {
            string strDirectoryname = Path.GetDirectoryName(strLogPath);

            if (false == Directory.Exists(strDirectoryname))
                Directory.CreateDirectory(strDirectoryname);
            return true;
        }
        catch (Exception)
        {
            return false;

        }
    }


    public virtual void Write(Exception ex) 
    {
        // Default 
    }

    public virtual void Write(string logText)
    { 
        // Default
    }
}

public class TxtFileLogger
    : BaseLogger
{
    public override void Write(Exception ex)
    {
        ErrorRoutine(ex);
        base.Write(ex);
    }

    public override void Write(string logText)
    {
        ErrorRoutine(logText);
        base.Write(logText);
    }

}