async public Task <CalculatorResponse> Post(CalculatorRequest exp)
        {
            string content = exp.Expression;

            if (!string.IsNullOrWhiteSpace(content))
            {
                float  value;
                string errMsg;
                if (EvalStrWorker.EvalStr(content, out value, out errMsg))
                {
                    _logger.LogInformation($"value: {value}");
                    return(new CalculatorResponse
                    {
                        StatusCode = System.Net.HttpStatusCode.OK,
                        Result = value.ToString()
                    });
                }
                else
                {
                    _logger.LogInformation($"errMsg: {errMsg}");
                    return(new CalculatorResponse
                    {
                        StatusCode = System.Net.HttpStatusCode.BadRequest,
                        ErrorMessage = errMsg
                    });
                }
            }
            return(new CalculatorResponse
            {
                StatusCode = System.Net.HttpStatusCode.BadRequest,
                ErrorMessage = "Expression can't be null."
            });
        }
        public async Task <HttpResponseMessage> Get()
        {
            string content = string.Empty;

            using (var reader = new StreamReader(Request.Body))
            {
                var body = await reader.ReadToEndAsync();

                _logger.LogInformation($"body: {body}");
                content = body;
            }
            if (!string.IsNullOrWhiteSpace(content))
            {
                float  value;
                string errMsg;
                if (EvalStrWorker.EvalStr(content, out value, out errMsg))
                {
                    _logger.LogInformation($"value: {value}");
                    return(new HttpResponseMessage
                    {
                        StatusCode = System.Net.HttpStatusCode.OK,
                        Content = new StringContent(value.ToString())
                    });
                }
                else
                {
                    _logger.LogInformation($"errMsg: {errMsg}");
                    return(new HttpResponseMessage
                    {
                        StatusCode = System.Net.HttpStatusCode.BadRequest,
                        Content = new StringContent(errMsg)
                    });
                }
            }
            return(new HttpResponseMessage
            {
                StatusCode = System.Net.HttpStatusCode.BadRequest,
                Content = new StringContent("Expression can't be null.")
            });
        }