如何从LINQ to Entities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();

在以下代码中，如何从CurrentStock获取toTraceString()？它目前未被解析。

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

- StackTrace

Answer 1

你不能这样做，因为你已经调用了ToList - 它不是基于 Linq-to-Entities 查询而是一个简单的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();

顺便问一下，你为什么使用dynamic而不是string？动态类型只适用于特定情况 - 这不是这种情况。

- Ladislav Mrnka