如何将LINQ查询结果存入自定义的AdjustmentsList类型对象

我来帮你搞定这个问题！问题的核心是你当前的LINQ查询返回的是匿名类型的List，而不是你自定义的Adjustments对象集合，所以没法直接转换成AdjustmentsList类型。下面给你几种简单的解决办法：

方法1：先生成Adjustments集合，再赋值给AdjustmentsList #

首先修改你的LINQ查询，直接创建Adjustments对象而不是匿名类型：

// 先获取Adjustments类型的列表
var adjustmentsItems = (from a in a1 
                        join fx in q on a.CurrencyCodeID equals fx.CurrencyCodeID 
                        select new Adjustments 
                        { 
                            AdjustmentID = a.AdjustmentID, 
                            AdjustmentTypeID = a.AdjustmentTypeID 
                        }).ToList();

// 实例化AdjustmentsList并赋值items属性
var day0Spot = new AdjustmentsList { items = adjustmentsItems };

方法2：一步到位实例化AdjustmentsList #

如果不想分开写，也可以直接在AdjustmentsList的初始化器里完成查询：

var day0Spot = new AdjustmentsList
{
    items = (from a in a1 
             join fx in q on a.CurrencyCodeID equals fx.CurrencyCodeID 
             select new Adjustments 
             { 
                 AdjustmentID = a.AdjustmentID, 
                 AdjustmentTypeID = a.AdjustmentTypeID 
             }).ToList()
};

方法3：给AdjustmentsList添加构造函数（更优雅的方式） #

你可以给AdjustmentsList类加一个接收List<Adjustments>的构造函数，这样后续使用会更方便：

class AdjustmentsList 
{ 
    public List<Adjustments> items = new List<Adjustments>();
    
    // 添加构造函数，直接传入Adjustments列表
    public AdjustmentsList(List<Adjustments> adjustments)
    {
        items = adjustments;
    }
}

之后使用的时候就可以这样写：

var day0Spot = new AdjustmentsList(
    (from a in a1 
     join fx in q on a.CurrencyCodeID equals fx.CurrencyCodeID 
     select new Adjustments 
     { 
         AdjustmentID = a.AdjustmentID, 
         AdjustmentTypeID = a.AdjustmentTypeID 
     }).ToList()
);

为什么原来的写法不行？ #

你之前的查询select new { a.AdjustmentID, a.AdjustmentTypeID }生成的是.NET自动创建的匿名类型，虽然它的属性和Adjustments一样，但本质上是完全不同的类型，所以无法直接赋值给AdjustmentsList的items（它需要的是List<Adjustments>）。所以必须在查询中明确创建Adjustments实例，才能正确存入自定义列表类型。

内容的提问来源于stack exchange，提问作者user1272386