c# - 如何使用 LINQ C# 过滤字典中的嵌套集合

Question

这是我的实体结构

Transaction Entity 

TransactionID, CompanyID  TransactionItems
  1             10           List<TransactionItems>
  2             10           List<TransactionItems>
  3             20           List<TransactionItems>

TransactionItems Entity

TransactionItemID TransactionID Value Postive Negative
1                  2            10    yes   
2                  2            20    yes
3                  2            30           yes   
4                  3            100          yes    
5                  3            200   yes   

I need to sum the values of Value based on positive or negative flag and then compute total like this

CompanyID Postive Negative
10          30     30
20          200    100

业务层函数返回Dictionary<int, List<Transaction>>基本上是这样的

Key         Value
CompanyID, List<Transaction>

到目前为止我只实现了这个

 _Transaction.GetCompanyTransactions().
                Select(_Company => new
                {
                    Company = _Company.Key,
                    Positive = 
                    Negative =
                });

谁能帮忙

Answer 1

您只需对列表中的值字段求和即可:

_Transaction.GetCompanyTransactions()
    .Select(g => new { 
        CompanyId = g.Key, 
        Positive = g.Value.SelectMany(t => t.TransactionItems).Where(t => t.Positive).Sum(t => t.Value), 
        Negative = g.Value.SelectMany(t => t.TransactionItems).Where(t => t.Negative).Sum(t => t.Value)})
        });