Linq 查询 - 列表中的列表 [重复]

Posted 2023-03-21

【中文标题】Linq 查询 - 列表中的列表 [重复]

【英文标题】：Linq query - List within List [duplicate]

【发布时间】：2018-01-05 17:38:55

【问题描述】：

我正在尝试选择一个包含Fund.Name 和List<Investment> 的列表。

var funds = new List<Fund>

    new Fund  Id = 1 , Name = "good" ,
    new Fund  Id = 2, Name = "bad" 
;

var investments = new List<Investment>

    new Investment  Fund = funds[0], Value = 100 ,
    new Investment  Fund = funds[0], Value = 200 ,
    new Investment  Fund = funds[1], Value = 300 
;

然后我尝试用这个来创建查询：

var query = from f in funds
            join i in investments
            on f.Id equals i.Fund.Id
            select new  f.Name, i ;

我想要这样的东西：

 Name = good,  Id = 1, Value = 100 ,  Id = 1, Value = 200 ,
 Name = bad,  Id = 2, Value = 300 

但我得到的是这样的：

 Name = good,  Id = 1, Value = 100 ,
 Name = good,  Id = 1, Value = 200 ,
 Name = bad,  Id = 2, Value = 300 

【参考方案1】：

尝试使用 GroupJoin。

var query = funds.GroupJoin(investments, f => f.Id, i => i.Fund.Id, (f, result) => new  f.Name, result );