C#怎样避免产生的随机数是重复的呢？

副源代码：

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Collections;

namespace 数组练习

{

    class Program

    {

        static void Main(string[] args)

        {

            int []a=new int [10];

            Random random=new Random();

            for (int i = 0; i < 10; i++)

            {

              a[i]=random.Next(20);

            }

           

                Console.WriteLine("产生的随机数列是:");

                for (int i = 0; i < 10; i++)

            Console.Write("{0} ",a[i]);

            Console.ReadKey();

        }

    }

}