c# - 如何从 linq 到实体查询中获取 toTraceString()？

Question

dynamic traceFile =  Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + "\\EntityFrameworkTrace.log";                
var CurrentStock = (from s in DBViews.StockStatus
                    where s.ProductID != 10
                    orderby s.ProductName
                    select new
                    {
                        s.ProductID,
                        s.ProductName,
                        CurrentStock = s.TotalStocked - s.TotalSold,
                        s.CurrentSellingRate,
                        CashValue = (s.TotalStocked - s.TotalSold) * s.CurrentSellingRate,
                        s.LastStocked,
                        s.LastCostPrice,
                        s.LastQtyStocked
                    }).ToList();

File.AppendAllText(traceFile, CurrentStock.toTraceString());   
return CurrentStock.ToList();

如何在下一行中从 CurrentStock 获取 toTraceString()？它没有得到解决

File.AppendAllText(traceFile,  CurrentStock.toTraceString()); 

Answer 1

你不能，因为你已经调用了 ToList - 它不是 Linq-to-Entities 查询，而只是一个 List 实例。

试试这个:

var CurrentStock = (from s in DBViews.StockStatus
                    where s.ProductID != 10
                    orderby s.ProductName
                    select new
                    {
                        s.ProductID,
                        s.ProductName,
                        CurrentStock = s.TotalStocked - s.TotalSold,
                        s.CurrentSellingRate,
                        CashValue = (s.TotalStocked - s.TotalSold) * s.CurrentSellingRate,
                        s.LastStocked,
                        s.LastCostPrice,
                        s.LastQtyStocked
                    }); // No ToList here!

File.AppendAllText(traceFile, ((ObjectQuery)CurrentStock).ToTraceString());   
return CurrentStock.ToList();

顺便说一句。为什么要使用 dynamic 而不是 string？动态类型仅适用于有意义的特殊情况 - 事实并非如此。