为什么 输出为1

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

namespace Question10
{
    class Program
    {
        static void Main(string[] args)
        {
            double i=1;
            double sum = 1;
            while(i<100)
            {
                sum=sum+i/(i+1);
                i++;
            }
            Console.WriteLine(sum);
        }
    }
}