C# 聚合查询上的实体框架左连接

我有一个EF查询，它包含许多聚合子查询（Count、Sum和Max）。有两个问题

我需要将子查询上的连接保留为左连接，这样即使聚合子查询中没有结果，也会返回记录。目前，仅当所有子查询返回记录时才返回记录

返回的批发商CustomerAndAgreegateOrders对象的结果列表包含一个联系人对象，该对象还需要包括地址和县。我在查询中添加了

Include（c=>c.Addresses.Select（a=>a.Country））

，但是联系人对象不包含任何地址对象

对于任何一个问题的任何帮助都将不胜感激。下面是完整的查询

var month1Date = DateTime.Today.AddMonths(-1);
var month3Date = DateTime.Today.AddMonths(-3);
var month6Date = DateTime.Today.AddMonths(-6);
var month12Date = DateTime.Today.AddMonths(-12);

var db = GetNewContext();
var qry = from c in db.Contacts
                      .Include(c => c.Addresses.Select(a => a.Country))
          join orderCount in
              (
                  from o in db.WholesaleOrders
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalOrders = g.Count()
                  }
              ) on c.Id equals orderCount.ContactId
          join month1Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month1Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month1Value.ContactId
          join month3Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month3Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month3Value.ContactId
          join month6Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month6Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month6Value.ContactId 
          join month12Value in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month12Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      TotalValue = g.Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price))
                  }
              ) on c.Id equals month12Value.ContactId
          join month12Quantity in
              (
                  from o in db.WholesaleOrders
                  where o.OrderDate >= month12Date
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      OrderCount = g.Count()
                  }
              ) on c.Id equals month12Quantity.ContactId
          join lastOrderDate in
              (
                  from o in db.WholesaleOrders
                  group o by o.ContactId into g
                  select new
                  {
                      ContactId = g.Key,
                      LastOrderDate = g.Max(r => r.OrderDate)
                  }
              ) on c.Id equals lastOrderDate.ContactId
          select new WholesaleCustomerAndAggregateOrders
          {
              Contact = c,
              TotalOrders = orderCount.TotalOrders,
              Month1Value = month1Value.TotalValue,
              Month3Value = month3Value.TotalValue,
              Month6Value = month6Value.TotalValue,
              Month12Value = month12Value.TotalValue,
              Month12OrderCount = month12Quantity.OrderCount,
              LastOrderDate = lastOrderDate.LastOrderDate
          };

return await qry.ToListAsync();

这个怎么样：

db.WholesaleOrders
    .GroupBy(o => o.ContactId)
    .Select(a => new { 
        a.Key, 
        TotalOrders = a.Count(),
        LastOrderDate = a.Max(r => r.OrderDate),
        Month1Value = a.Where(b => b.OrderDate >= month1Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price),
        Month3Value = a.Where(b => b.OrderDate >= month3Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price),
        Month6Value = a.Where(b => b.OrderDate >= month6Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price),
        Month12Value = a.Where(b => b.OrderDate >= month12Date).Sum(r => r.LineItems.Sum(l => l.QuantityOrdered * l.Price)
        }).ToListAsync();

更新：向投影添加另一个属性：

Addresses = db.Addresses.Where(ad => ad.ContactId == a.Key);

其中db是您的上下文，ad.ContactId是地址表中联系人的FK

---

要使其正常工作，必须将连接的multipleactiveresultsets属性设置为True。

如果在一个方法中只有一个

Wait

，则不要将

async

与

return Wait

一起使用，返回任务本身，这确实更有效。您好，谢谢。这解决了聚合问题，这是向前迈出的一大步。但是，Contact仍然不会返回填充的地址集合。为了解决这个问题，我正在执行第二个查询，以提取具有地址和国家/地区的联系人，然后将联系人添加到批发商CustomerAndAggregateOrder对象中。如果有人知道如何做这是一个单一的查询，请分享。