Method calculate

tutorial/netstd/Server/Program.cs:399–453

(int logid, Work? w, CancellationToken cancellationToken)

            }

            public async Task<int> calculate(int logid, Work? w, CancellationToken cancellationToken)
            {
                if (Logger.IsEnabled(LogLevel.Information))
                    Logger.LogInformation("Calculate({logid}, [{w.Op},{w.Num1},{w.Num2}])", logid, w?.Op, w?.Num1, w?.Num2);

                int val;
                switch (w?.Op)
                {
                    case Operation.ADD:
                        val = w.Num1 + w.Num2;
                        break;

                    case Operation.SUBTRACT:
                        val = w.Num1 - w.Num2;
                        break;

                    case Operation.MULTIPLY:
                        val = w.Num1 * w.Num2;
                        break;

                    case Operation.DIVIDE:
                        if (w.Num2 == 0)
                        {
                            var io = new InvalidOperation
                            {
                                WhatOp = (int) w.Op,
                                Why = "Cannot divide by 0"
                            };

                            throw io;
                        }
                        val = w.Num1 / w.Num2;
                        break;

                    default:
                    {
                        var io = new InvalidOperation
                        {
                            WhatOp = ((int?)w?.Op) ?? -1,
                            Why = "Unknown operation"
                        };

                        throw io;
                    }
                }

                var entry = new SharedStruct
                {
                    Key = logid,
                    Value = val.ToString()
                };

                _log[logid] = entry;
                return val;
            }

            public async Task zip(CancellationToken cancellationToken)
            {