FileWatcher/code/src/Logger.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FileWatcher
{
    public sealed class Logger
    {
        private delegate void SetTextCallback(string str, Color? color);

        #region Singleton

        private static readonly Logger instance = new Logger();

        static Logger()
        {
        }

        public static Logger Instance
        {
            get
            {
                return instance;
            }
        }
        #endregion

        private Logger()
        {
        }

        public void Print(string str, Color? color = null)
        {
            if (Form1.Instance.textBox2.InvokeRequired)
            {
                SetTextCallback d = new SetTextCallback(Print);
                Form1.Instance.textBox2.Invoke(d, new object[] { str, color });
            }
            else
            {
                Form1.Instance.textBox2.AppendText(str, color.HasValue ? color.Value : Color.Black);
                Form1.Instance.textBox2.SelectionStart = Form1.Instance.textBox2.Text.Length;
                Form1.Instance.textBox2.ScrollToCaret();
            }
        }

        public void PrintLine(string str, Color? color = null)
        {
            if (Form1.Instance.textBox2.InvokeRequired)
            {
                SetTextCallback d = new SetTextCallback(PrintLine);
                Form1.Instance.textBox2.Invoke(d, new object[] { str, color });
            }
            else
            {
                Form1.Instance.textBox2.AppendText(str + Environment.NewLine, color.HasValue ? color.Value : Color.Black);
                Form1.Instance.textBox2.SelectionStart = Form1.Instance.textBox2.Text.Length;
                Form1.Instance.textBox2.ScrollToCaret();
            }
        }

        public void ErrorLine(string str, Color? color = null)
        {
            if (Form1.Instance.textBox2.InvokeRequired)
            {
                SetTextCallback d = new SetTextCallback(ErrorLine);
                Form1.Instance.textBox2.Invoke(d, new object[] { str, color });
            }
            else
            {
                Form1.Instance.textBox2.AppendText(str + Environment.NewLine, color.HasValue ? color.Value : Color.Red);
                Form1.Instance.textBox2.SelectionStart = Form1.Instance.textBox2.Text.Length;
                Form1.Instance.textBox2.ScrollToCaret();
            }
        }

        public void LogLine(string str)
        {
            Print(DateTime.Now.ToString("R") + " ", Color.Maroon);
            PrintLine(str);
        }

        public void LogErrorLine(string str)
        {
            Print(DateTime.Now.ToString("R") + " ", Color.Maroon);
            PrintLine(str, Color.Red);
        }

        static public void WriteLine(string str)
        {
            Logger.Instance.PrintLine(str);
        }

        static public void Error(string str)
        {
            Logger.Instance.ErrorLine(str);
        }

        static public void Log(string str)
        {
            Logger.Instance.LogLine(str);
        }

        static public void LogError(string str)
        {
            Logger.Instance.LogErrorLine(str);
        }
    }
}