LINQ to Objects连接两个集合以在第一个集合中设置值 [英] LINQ to Objects Join two collections to set values in the first collection

问题描述

我有以下实体框架查询:

I have the following Entity Framework query:

var results = from r in db.Results
              select r;

我正在使用AutoMapper映射到另一种类型:

I'm using AutoMapper to map to another type:

var mapped = Mapper.Map<IEnumerable<Database.Result>, IEnumerable<Objects.Result>>(results);

在我的Objects.Result类型中，我有一个名为reason的属性，该属性不是来自数据库.它来自另一个需要基本填充回映射类型的来源:

In my Objects.Result type, I have a property called reason that is not coming from the database. It is coming from another source that I need to basically populate back into my mapped type:

var reasons = new List<Reason>
{
    new Reason { Id = 1, Reason = "asdf..." }
};

我需要将原因与我的映射集合一起加入，并使用我的原因集合中的值在映射集合中设置Reason属性.这可能吗?

I need to join the reasons with my mapped collection and set the Reason property in my mapped collection using the value from my reasons collection. Is this possible?

 // need something like this:
 mapped = from m in mapped
          join r in reasons on m.Id equals r.Id
          update m.Reason = r.Reason
          select m;

显然上述代码无法编译，但是我可以编写满足我要求的代码吗?

Obviously the above code doesn't compile, but is there code I can write that does what I want?

推荐答案

循环进行突变.理想情况下，Linq应该对其操作的集合没有任何变异.使用Linq筛选，排序，投影数据，使用传统技术进行修改.

Do the mutation in a loop. Optimally, Linq should be free of mutations to the collection(s) it operates against. Use Linq to filter, order, project your data, use traditional techniques to modify.

var joinedData = from m in mapped 
                 join r in reasons on m.Id equals r.Id 
                 select new { m, r };

foreach (var item in joinedData)
{
    item.m.Reason = item.r.Reason;
}

这篇关于LINQ to Objects连接两个集合以在第一个集合中设置值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！