在实体框架中使用Join,Group By和Sum

Question

我的模特看起来像:

public class ReturnItem
{
    public int returnItemId { get ; set; }
    public int returnRequestId { get; set; }
    public int quantity { get; set; }
    public string item { get; set; }
}

public class ReturnRequest
{
    public int returnRequestId { get; set; }
    public string orderNumber  { get; set; }
    public IEnumerable<ReturnItem> returnItems { get; set; }
}

我有以下查询:

SELECT item, sum(quantity)
FROM ReturnItem
JOIN ReturnRequest
ON ReturnRequest.returnRequestId = ReturnItem.returnRequestId
WHERE ReturnRequest.orderNumber = '1XX'
GROUP BY item

如何将查询转换为Entity Framework并返回List<ReturnItem>？我可以用.Include而不是.Join吗？

Answer 1

from ri in db.ReturnItems
join rr in db.ReturnRequests
   on ri.returnRequestId equals rr.returnRequestId
where rr.orderNumber == "1XX"
group ri by ri.item into g
select new {
   Item = g.Key,
   Quantity = g.Sum(i => i.quantity)
}

你不能使用Include而不是Join因为Include翻译成左外连接但你需要内部加入.

但您可以使用navigation属性隐式执行连接:

db.ReturnRequests
  .Where(rr => rr.orderNumber == "1XX")
  .SelectMany(rr => rr.returnItems)
  .GroupBy(ri => ri.item)
  .Select(g => new {
      Item = g.Key,
      Quantity = g.Sum(ri => ri.quantity)
  });