C#随机生成不重复字符串

今天整理以前一个项目源码，发现两个随机生成不重复字符串的方法，觉得用起来挺方便的，在此贴出来，方便以后查阅。

        方法一：随机生成不重复数字字符串

       private int rep=0;

       /// <summary>
       /// 生成随机数字字符串
       /// </summary>
       /// <param name="codeCount">待生成的位数</param>
       /// <returns>生成的数字字符串</returns>
       private string GenerateCheckCodeNum(int codeCount)
       {
           string str = string.Empty;
           long num2 = DateTime.Now.Ticks + this.rep;
           this.rep++;
           Random random = new Random(((int)(((ulong)num2) & 0xffffffffL)) | ((int)(num2 >> this.rep)));
           for (int i = 0; i < codeCount; i++)
           {
               int num = random.Next();
               str = str + ((char)(0x30 + ((ushort)(num % 10)))).ToString();
           }
           return str;
       }

        方法二：随机生成字符串（数字和字母混和）

       /// <summary>
       /// 生成随机字母字符串(数字字母混和)
       /// </summary>
       /// <param name="codeCount">待生成的位数</param>
       /// <returns>生成的字母字符串</returns>
       private string GenerateCheckCode(int codeCount)
       {
           string str = string.Empty;
           long num2 = DateTime.Now.Ticks + this.rep;
           this.rep++;
           Random random = new Random(((int)(((ulong)num2) & 0xffffffffL)) | ((int)(num2 >> this.rep)));
           for (int i = 0; i < codeCount; i++)
           {
               char ch;
               int num = random.Next();
               if ((num % 2) == 0)
               {
                   ch = (char)(0x30 + ((ushort)(num % 10)));
               }
               else
               {
                   ch = (char)(0x41 + ((ushort)(num % 0x1a)));
               }
               str = str + ch.ToString();
           }
           return str;
       }