Question

我有一个Orders表和一个Assignments表，我使用LINQ to Entities连接在一起。每个订单都有产品和数量。每个订单都有多个分配数量。我想输出以下内容：

订单：

ID | OrderCode | Quantity | Other Columns...
1  | 30000-1   | 3        | ...
2  | 41000-7   | 2        | ...

作业：

OrderID | Assignment | Other Columns...
1       | 4526       | ...
2       | 2661       | ...
2       | 5412       | ...

我想输出一个表格，如：

OrderCode | Assignment
30000-1   | 4526
30000-1   | 
30000-1   |
41000-7   | 2661
41000-7   | 5412

欢迎任何建议！

Answer 1

我会将任务分成三部分。

首先，我使用LINQ to Entities获取完整的订单集合，每个订单都有相应的分配集合：

var a = (from o in orders
         join a in assignments on s.Id equals a.OrderId into oa
         //Notice that I use oa.DefaultIfEmpty().  This essentially the way to do a
         //LEFT JOIN in LINQ.  You'll want to do a LEFT JOIN if you don't
         //want to exclude order codes that have no assignments
         select new { o.OrderCode, o.Quantity, Assignments = oa.DefaultIfEmpty() })
        .ToList();

a会为您的示例返回以下内容：

OrderCode | Assignment
30000-1   | 4526
41000-7   | 2661
41000-7   | 5412

然后我会添加“缺失”行

var b = a.SelectMany(o => 
{
    var numOrdersInList = o.Count(o2 => o2.OrderCode == o.OrderCode);
    return Enumerable.Range(0, o.Quantity - numOrdersInList)
                     .Select(i => new 
                                 { 
                                     o.OrderCode, 
                                     Assignment = Enumerable.Empty<Assignment>() 
                                 });
});

b会为您的示例返回以下内容：

OrderCode | Assignment
30000-1   | 
30000-1   |

然后我会把这两个枚举点连接起来。

var c = a.Select(o => new { o.OrderCode, o.Assignment })
         .Concat(b);

最后，连接应该返回您对示例的期望：

OrderCode | Assignment
30000-1   | 4526
30000-1   | 
30000-1   |
41000-7   | 2661
41000-7   | 5412

如何根据单元格中的数量复制行？ LINQ to Entities

1 个答案: