生成不重复的随机数 （验证码、随机密码等）

generate-random-string-num.cs

using System;
					
public class Program
{
	private const string VCHAR = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";
	private const string VNUM = "0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9";

	public static void Main()
	{
		Console.WriteLine(RndNum(16));
	}
	
	 /// <summary>
        /// 生成随机字符串
        /// </summary>
        /// <param name="len"></param>
        /// <returns></returns>
        public static string RndChar(int len)
        {
            return Rnd(VCHAR, len);
        }

        /// <summary>
        /// 生成随机数字
        /// </summary>
        /// <param name="len"></param>
        /// <returns></returns>
        public static string RndNum(int len)
        {
            return Rnd(VNUM, len);
        }

        /// <summary>
        /// 该方法根据给定集合， 用于生成指定位数的随机字符串或随机数字
        /// </summary>
        /// <param name="VcodeNum">参数是随机数的位数</param>
        /// <returns>返回一个随机数字符串</returns>
        private static string Rnd(string vcodes, int VcodeNum)
        {
            //验证码可以显示的字符集合
            string[] VcArray = vcodes.Split(new Char[] { ',' });//拆分成数组
            string code = "";//产生的随机数
            int temp = -1;//记录上次随机数值，尽量避避免生产几个一样的随机数

            System.Random rand = new System.Random();
            //采用一个简单的算法以保证生成随机数的不同
            for (int i = 1; i < VcodeNum + 1; i++)
            {
                if (temp != -1)
                {
                    rand = new System.Random(i * temp * unchecked((int)DateTime.Now.Ticks));//初始化随机类
                }
                int t = rand.Next(27);//获取随机数
                if (temp != -1 && temp == t)
                {
                    return Rnd(vcodes, VcodeNum);//如果获取的随机数重复，则递归调用
                }
                temp = t;//把本次产生的随机数记录起来
                code += VcArray[t];//随机数的位数加一
            }
            return code;
        }
    
}