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Uğraşmayın boş laflara ve yazılara direk kod C# ShortUrl

public static class ShortUrl
    {
        private const string ShorturlCharsLcase = "abcdefgijkmnopqrstwxyz";
        private const string ShorturlCharsUcase = "ABCDEFGHJKLMNPQRSTWXYZ";
        private const string ShorturlCharsNumeric = "23456789";

        public static string RandomCharacters()
        {
            var charGroups = new[]
                                 {
                ShorturlCharsLcase.ToCharArray(),
                ShorturlCharsUcase.ToCharArray(),
                ShorturlCharsNumeric.ToCharArray()
            };

            var charsLeftInGroup = new int[charGroups.Length];

            for (var i = 0; i < charsLeftInGroup.Length; i++)
                charsLeftInGroup[i] = charGroups[i].Length;

            var leftGroupsOrder = new int[charGroups.Length];

            for (var i = 0; i < leftGroupsOrder.Length; i++)
                leftGroupsOrder[i] = i;

            var randomBytes = new byte[4];
            var rng = new RNGCryptoServiceProvider();

            rng.GetBytes(randomBytes);

            var seed = (randomBytes[0] & 0x7f) << 24 | randomBytes[1] << 16 | randomBytes[2] << 8 | randomBytes[3];
            var random = new Random(seed);
            var shortUrl = new char[random.Next(8, 8)];
            var lastLeftGroupsOrderIdx = leftGroupsOrder.Length - 1;

            for (var i = 0; i < shortUrl.Length; i++)
            {
                int nextLeftGroupsOrderIdx;

                if (lastLeftGroupsOrderIdx == 0)
                    nextLeftGroupsOrderIdx = 0;
                else
                    nextLeftGroupsOrderIdx = random.Next(0,
                                                         lastLeftGroupsOrderIdx);

                var nextGroupIdx = leftGroupsOrder[nextLeftGroupsOrderIdx];
                var lastCharIdx = charsLeftInGroup[nextGroupIdx] - 1;
                var nextCharIdx = lastCharIdx == 0 ? 0 : random.Next(0, lastCharIdx + 1);

                shortUrl[i] = charGroups[nextGroupIdx][nextCharIdx];

                if (lastCharIdx == 0)
                    charsLeftInGroup[nextGroupIdx] = charGroups[nextGroupIdx].Length;
                else
                {
                    if (lastCharIdx != nextCharIdx)
                    {
                        var temp = charGroups[nextGroupIdx][lastCharIdx];

                        charGroups[nextGroupIdx][lastCharIdx] = charGroups[nextGroupIdx][nextCharIdx];
                        charGroups[nextGroupIdx][nextCharIdx] = temp;
                    }

                    charsLeftInGroup[nextGroupIdx]--;
                }

                if (lastLeftGroupsOrderIdx == 0)
                    lastLeftGroupsOrderIdx = leftGroupsOrder.Length - 1;
                else
                {
                    if (lastLeftGroupsOrderIdx != nextLeftGroupsOrderIdx)
                    {
                        var temp = leftGroupsOrder[lastLeftGroupsOrderIdx];

                        leftGroupsOrder[lastLeftGroupsOrderIdx] = leftGroupsOrder[nextLeftGroupsOrderIdx];
                        leftGroupsOrder[nextLeftGroupsOrderIdx] = temp;
                    }

                    lastLeftGroupsOrderIdx--;
                }
            }

            return new string(shortUrl);
        }
    }