linq - join 子句中的表达式之一的类型不正确。对“组加入”的调用中的类型推断失败

Question

var val1 =
                (from main in
                     (from irac in objIRAC
                      join iip in objIIP on irac.InvoiceItemID equals iip.InvoiceItemID
                      join oritc in
                          (from ritc in objRITC
                           join iips in objIIP on ritc.InvoiceItemPremiumID equals iips.InvoiceItemPremiumID
                           where ritc.ReconID == ReconId 
                                 && ritc.BookOfBusinessInvoiceItemPremiumID == BookOfBusinessInvoiceItemPremiumID 
                                 && ritc.InvoiceID == InvoiceId 
                           group new { ritc, iips } by new { ritc.ReconID, iips.InvoiceItemID }
                               into ritcs
                               select new
                               {
                                   ritcs.Key.ReconID,
                                   ritcs.Key.InvoiceItemID
                               }) on ReconId equals oritc.ReconID into oritcs // ReconId
                      from oritc in oritcs.DefaultIfEmpty()
                      where iip.InvoiceItemPremiumID == BookOfBusinessInvoiceItemPremiumID 
                      select new
                      {
                          oritc.InvoiceItemID,
                          irac.CommissionOnTypeID,
                          irac.BOBFamilyID,
                          irac.RateTypeID,
                          irac.Rate,
                          irac.CommissionAdjustmentFlag
                      })
                 join sub in objIRAC // Here getting the error
                 on new { main.InvoiceItemID, main.CommissionOnTypeID, main.BOBFamilyID, main.RateTypeID, main.Rate, main.CommissionAdjustmentFlag }
                 equals new { sub.InvoiceItemID, sub.CommissionOnTypeID, sub.BOBFamilyID, sub.RateTypeID, sub.Rate, sub.CommissionAdjustmentFlag }
                 into subs
                 from osub in subs.DefaultIfEmpty()
                 select new { osub.InvoiceItemID });

Answer 1

检查类型

main.InvoiceItemID, main.CommissionOnTypeID, main.BOBFamilyID, main.RateTypeID, main.Rate, main.CommissionAdjustmentFlag

和

sub.InvoiceItemID, sub.CommissionOnTypeID, sub.BOBFamilyID, sub.RateTypeID, sub.Rate, sub.CommissionAdjustmentFlag

它们应该完全匹配。即：如果一个属性是 aNullable<int>而对应的属性是int它不匹配。由于所有属性但InvoiceItemID都来自同一个实体 InvoiceItemID 可能是罪魁祸首。

Answer 2

赔率是您的外键引用之一是可以为空的，您需要进行显式转换才能使联接（假定内部联接）起作用。

var result =
  from a in context.T1
  join b in context.T2
    on new { s.Field1, s.Field2 }
    equals new { 
      Field1 = (int)b.T3.Field1 /* Join via sub-table, explicit conversion from int? to int  */
      ,Field2 = (int)b.Field2 /* explicit conversion from int? to int  */
    }
  where 
    b.T3.Field1 != null /* Specify no nulls allowed for inner-join fields */
    && b.Field2 != null
    && b.Field3 == InputVar1 /* Input Search Variables */
    && b.Field4 == InputVar2
  select a;

上面的示例是从我正在使用的实际查询中重命名的。