using system
class welcome
{
    static void Main()
    {
        Console.WriteLine("please enter you name");
        Console.Readline();
        Console.Writeline("welcome to you!");
    }
}

using System;
using System.Collections.Generic;
using System.Text;

namespace testContest
{
    class welcome
    {
       static void Main()
       {
           Console.WriteLine("please enter you name");
           Console.ReadLine();
           Console.WriteLine("welcome to you!");
       }
    }
}

注意大小写问题，你copy的代码也太离谱了，缺胳膊少腿的，下次注意咯。