Linq to Entities Group Sum計算的屬性

Question

使用C＃4和EF5。

有麻煩，試圖總結計算特性：

The specified type member 'QtyAvailable' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported. 

下面是屬性定義：

public decimal QtyAvailable 
    { 
     get 
     { return this.QtyInContainer - this.QtyAllocated; } 
    } 

這裏是LINQ的：

var viewModel = 
       companyItems 
         .GroupJoin(
          inventory, 
          items => items.Id, 
          inven => inven.ItemId, (im, icd) => new { im, icd } 
          ) 
         .SelectMany(
          itemInven => itemInven.icd.DefaultIfEmpty(), 
          (im, icd) => new { im, icd } 
         ) 
         .GroupBy(g => new 
          { 
           g.im.im.Id 
          } 
         ) 
         .Select(group => 
           new ItemAvailabilityViewModel() 
           { 
            Id = group.Key.Id, 
            QtyAvailable = group.Sum(jt => jt.icd == null ? 0 : jt.icd.QtyAvailable), 
            UnitCashPrice = group.Max(jt => jt.im.im.UnitSellPrice), 
            UnitCreditPrice = group.Max(jt => jt.im.im.UnitSellPrice * (1 + company.CashDiscountPct)), 
            CustomerUnitPrice = group.Max(jt => jt.im.im.UnitSellPrice * (1 + decCreditPriceMarkup)) 
           } 
         ) 
         ; 

不知道如何實現這個結果。我需要以某種方式將其分解爲2個查詢嗎？

Answer 1

看起來像把這個分解成2個查詢就是票。從我猜想發生的事情來看，第一次，當你調用.ToList（）時，它解析了計算的屬性，使得它本質上不再爲第二個查詢計算然後求和。這裏是結果代碼：

//join of Recpt Header and Detail 
      var unGroupedJoin = 
       companyItems 
         .GroupJoin(
          inventory, 
          items => items.Id, 
          inven => inven.ItemId, (im, icd) => new { im, icd } 
          ) 
         .SelectMany(
          itemInven => itemInven.icd.DefaultIfEmpty(), 
          (im, icd) => new { im, icd } 
         ).ToList(); 

      var viewModel = 
       unGroupedJoin 
         .GroupBy(g => new 
          { 
           g.im.im.Id 
          } 
         ) 
         .Select(group => 
           new ItemAvailabilityViewModel() 
           { 
            Id = group.Key.Id, 
            QtyAvailable = group.Sum(jt => jt.icd == null ? 0 : jt.icd.QtyAvailable), 
            UnitCashPrice = group.Max(jt => jt.im.im.UnitSellPrice), 
            UnitCreditPrice = group.Max(jt => jt.im.im.UnitSellPrice * (1 + company.CashDiscountPct)), 
            CustomerUnitPrice = group.Max(jt => jt.im.im.UnitSellPrice * (1 + decCreditPriceMarkup)) 
           } 
         ).ToList() 
         ;