using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Diagnostics;

 abstract class Maths
{
   public abstract int sum(int x ,int y);
}


 class ArithmeticOperation : Maths
{
    public override int sum(int x, int y) 
    {
          return (x+y);
    }
}

namespace WindowsFormsApplication2
{
    static class Program
    {
        /// <summary>
        /// 應用程式的主入口點。
        /// </summary>
        [STAThread]
        static void Main()
        {
            ArithmeticOperation temp = new ArithmeticOperation();
            int a=temp.sum(100, 100);


         //  Trace.Listeners.Clear();
           bool someBool = true;
           Trace.Listeners.Add(new TextWriterTraceListener(@"D:\MyListener.log")); 
           Trace.AutoFlush = true;//每次寫入日誌後是否都將其儲存到磁碟中

           Trace.WriteLine(DateTime.Now.ToString() + "--Enter function LogTest");
           Trace.Indent(); //縮排+1
           Trace.WriteLine("This is indented once");
           Trace.Indent();
           Trace.WriteLineIf(someBool, "Only written if someBool is true");
           Trace.Unindent(); //縮排-1
           Trace.Unindent();
           Trace.WriteLine("Leave function LogTest");
           Trace.Flush();//立即輸出

            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}
 

執行結果：