我试图在EF Core 3.0中构建一个查询,从数据库服务器获取完整的过程。
IEnumerable<int> stIds = stateIds;
var rtables = await db.Order.
Join(db.OrderDetail, order => order.OrderId, orderdetail => orderdetail.OrderId, (order, orderdetail) => new { order, orderdetail }).
Where(x => x.order.SellerId == sellerId && stIds.Contains(x.orderdetail.OrderStateId)&&x.order.RtableId != null)
.GroupBy(x =>
x.order.RtableId
)
.Select(x => new RtableState { RtableId = x.Key ?? 0, OrderStateId = x.OrderByDescending(x => x.orderdetail.OrderStateId).Select(x => x.orderdetail.OrderStateId).FirstOrDefault() }).ToListAsync();
我遇到了以下错误:
{ "Message": "使用 LINQ 表达式 'AsQueryable<<>f__AnonymousType52>(OrderByDescending<<>f__AnonymousType52, int>(\r\n source: NavigationTreeExpression\r\n Value: default(IGrouping, <>f__AnonymousType52>)\r\n Expression: (Unhandled parameter: e), \r\n keySelector: (x) => x.orderdetail.OrderStateId))' 时,'NavigationExpandingExpressionVisitor' 处理失败。这可能表明 EF Core 中存在错误或限制。有关更详细的信息,请参见 https://go.microsoft.com/fwlink/?linkid=2101433。", "Inner": "" }
我知道查询对于 EF Core 3.0 来说过于复杂,但这是一个错误还是不能正常工作?
我的解决方案是拆分请求。
IEnumerable<int> stIds = stateIds;
var rtableStatesServer = await db.Order.
Join(db.OrderDetail, order => order.OrderId, orderdetail => orderdetail.OrderId, (order, orderdetail) => new { order, orderdetail }).
Where(x => x.order.SellerId == sellerId && stIds.Contains(x.orderdetail.OrderStateId) && x.order.RtableId != null)
.GroupBy(x => new RtableState
{
RtableId =
x.order.RtableId ?? 0,
OrderStateId = x.orderdetail.OrderStateId
})
.Select(x => new RtableState { RtableId = x.Key.RtableId, OrderStateId = x.Key.OrderStateId }).ToListAsync();
var rtableStates = rtableStatesServer.GroupBy(r => r.RtableId,
(key, value) => new RtableState
{
RtableId = key,
OrderStateId = value.OrderByDescending(x=>x.OrderStateId).Select(x => x.OrderStateId).FirstOrDefault()
}).ToList();