private string GetRandomCode()
        {
            char[] chars = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

            string code = string.Empty;

            for (int i = 0; i < 4; i++)
            {
                Random rnd = new Random(GetRandomSeed());
                code += chars[rnd.Next(0, 10)].ToString();
            }

            return code;
        }

        private int GetRandomSeed()
        {
            byte[] bytes = new byte[4];
            System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
            rng.GetBytes(bytes);
            return BitConverter.ToInt32(bytes, 0);
        }

------解决方案--------------------


看看注释
C# code
   private string GetRandomCode()
        {
            char[] chars = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };  //随机数范围，填上字母就会生成字母

            string code = string.Empty;

            for (int i = 0; i < 4; i++) //4是生成多少位的随机数，自己可以改
            {
                Random rnd = new Random(GetRandomSeed());
                code += chars[rnd.Next(0, 10)].ToString();
            }

            return code;
        }

        private int GetRandomSeed()
        {
            byte[] bytes = new byte[4];
            System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
            rng.GetBytes(bytes);
            return BitConverter.ToInt32(bytes, 0);
        }