c# - Linq - 条件包含()

Question

我有以下方法根据参数中指定的条件过滤商店:

public int[] GetShopIds(IEnumerable<Guid> OrderCreaatorIds, IEnumerable<Guid> OrderItemCategoryIds, int StatusId)
    {
        var query = from s in _db.Shops
                    join o in _db.Orders on s.Id equals o.ShopId
                    join oi in _db.OrderItems on o.Id equals oi.OrderId
                    where
                    OrderCreaatorIds.Contains(o.CreatorId)
                    && OrderItemCategoryIds.Contains(oi.CategoryId)
                    && (int)o.StatusId == StatusId
                    select s.Id;

        return query.ToArray();
    }

事情是:OrderCreaatorIds，OrderItemCategoryIds 可以是 null 和 StatusId 可以是 0。在那种情况下，我不想有那些 where 子句，例如如果 OrderCreaatorIds 为 null，则查询应按如下方式工作:

public int[] GetShopIds(IEnumerable<Guid> OrderCreaatorIds, IEnumerable<Guid> OrderItemCategoryIds, int StatusId)
    {
        var query = from s in _db.Shops
                    join o in _db.Orders on s.Id equals o.ShopId
                    join oi in _db.OrderItems on o.Id equals oi.OrderId
                    where
                    OrderItemCategoryIds.Contains(oi.CategoryId)
                    && (int)o.StatusId == StatusId
                    select s.Id;

        return query.ToArray();
    }

等等

不幸的是 OrderCreaatorIds != null && OrderCreaatorIds.Contains(o.CreatorId) 不工作。

Answer 1

public int[] GetShopIds(IEnumerable<Guid> OrderCreaatorIds, IEnumerable<Guid> OrderItemCategoryIds, int StatusId)
{
    var query = from s in _db.Shops
        join o in _db.Orders on s.Id equals o.ShopId
        join oi in _db.OrderItems on o.Id equals oi.OrderId
        select new { s = s, o = o, oi = oi };

    if (null != OrderCreaatorIds)
        query = query.Where(x_ => OrderCreaatorIds.Contains(x_.o.CreatorId));

    if (null != OrderItemCategoryIds)
        query = query.Where(x_ => OrderItemCategoryIds.Contains(x_.oi.CategoryId));

    if (0 < StatusId)
        query = query.Where(x_ => (int)x_.o.StatusId == StatusId);

    return query.select(x_ => x_.s.Id).ToArray();
}

也许您必须向 IQueryable<> 添加一些转换以使其可编译。我没有在编译器中检查它。