System.Data.Common.UInt16Storage.Aggregate C# (CSharp) Метод

        public override object Aggregate(int[] records, AggregateType kind)
        {
            bool hasData = false;
            try
            {
                switch (kind)
                {
                    case AggregateType.Sum:
                        ulong sum = s_defaultValue;
                        foreach (int record in records)
                        {
                            if (HasValue(record))
                            {
                                checked { sum += _values[record]; }
                                hasData = true;
                            }
                        }
                        if (hasData)
                        {
                            return sum;
                        }
                        return _nullValue;

                    case AggregateType.Mean:
                        long meanSum = s_defaultValue;
                        int meanCount = 0;
                        foreach (int record in records)
                        {
                            if (HasValue(record))
                            {
                                checked { meanSum += _values[record]; }
                                meanCount++;
                                hasData = true;
                            }
                        }
                        if (hasData)
                        {
                            ushort mean;
                            checked { mean = (ushort)(meanSum / meanCount); }
                            return mean;
                        }
                        return _nullValue;

                    case AggregateType.Var:
                    case AggregateType.StDev:
                        int count = 0;
                        double var = 0.0f;
                        double prec = 0.0f;
                        double dsum = 0.0f;
                        double sqrsum = 0.0f;

                        foreach (int record in records)
                        {
                            if (HasValue(record))
                            {
                                dsum += _values[record];
                                sqrsum += _values[record] * (double)_values[record];
                                count++;
                            }
                        }

                        if (count > 1)
                        {
                            var = count * sqrsum - (dsum * dsum);
                            prec = var / (dsum * dsum);

                            // we are dealing with the risk of a cancellation error
                            // double is guaranteed only for 15 digits so a difference
                            // with a result less than 1e-15 should be considered as zero

                            if ((prec < 1e-15) || (var < 0))
                                var = 0;
                            else
                                var = var / (count * (count - 1));

                            if (kind == AggregateType.StDev)
                            {
                                return Math.Sqrt(var);
                            }
                            return var;
                        }
                        return _nullValue;

                    case AggregateType.Min:
                        ushort min = ushort.MaxValue;
                        for (int i = 0; i < records.Length; i++)
                        {
                            int record = records[i];
                            if (HasValue(record))
                            {
                                min = Math.Min(_values[record], min);
                                hasData = true;
                            }
                        }
                        if (hasData)
                        {
                            return min;
                        }
                        return _nullValue;

                    case AggregateType.Max:
                        ushort max = ushort.MinValue;
                        for (int i = 0; i < records.Length; i++)
                        {
                            int record = records[i];
                            if (HasValue(record))
                            {
                                max = Math.Max(_values[record], max);
                                hasData = true;
                            }
                        }
                        if (hasData)
                        {
                            return max;
                        }
                        return _nullValue;

                    case AggregateType.First:
                        if (records.Length > 0)
                        {
                            return _values[records[0]];
                        }
                        return null;

                    case AggregateType.Count:
                        count = 0;
                        for (int i = 0; i < records.Length; i++)
                        {
                            if (HasValue(records[i]))
                            {
                                count++;
                            }
                        }
                        return count;
                }
            }
            catch (OverflowException)
            {
                throw ExprException.Overflow(typeof(ushort));
            }
            throw ExceptionBuilder.AggregateException(kind, _dataType);
        }