展开具有嵌套对象集合的LINQ集合对象 [英] Flatten LINQ collection object with nested object collections

问题描述

这是一个棘手的问题。我试图压平一个LINQ对象集合。集合中的每个项目都有可能拥有两个其他对象的集合。见下面的例子。

This is a tricky one. I an trying to flatten a LINQ object collection. Each item in the collection has the potential of having two collections of other objects. See the example below.

public class DemoClass
{
    public string Name {get; set;}
    public string Address {get; set;}
    public List<Foo> Foos = new List<Foo>();
    public List<Bar> Bars = new List<Bars>();
}

我一直在做的是使用这个代码块展开这个对象

What I had been doing is this using this code block to flatten this object

var output = from d in DemoClassCollection
    from f in d.Foos
    from b in d.Bars
    select new {
        d.Name, 
        d.Address,
        f.FooField1, 
        f.FooField2, 
        b.BarField1,
        b.BarField2
    };

但我遇到的问题是，我得到的结果是 >那些在Foos和Bars集合中有对象的DemoClass对象。我需要获取DemoClass中的所有对象，无论在Foos和Bars集合中是否有对象。

But the problem I'm having is that the result I get is only those DemoClass objects that have objects in the Foos and Bars collections. I need to get all objects in the DemoClass regardless if there are objects in the Foos and Bars collections.

任何帮助都将非常感激。

Any help would be greatly appreciated.

谢谢！

推荐答案

听起来你可能想使用 DefaultIfEmpty ：

var output = from d in DemoClassCollection
    from f in d.Foos.DefaultIfEmpty()
    from b in d.Bars.DefaultIfEmpty()
    select new {
        d.Name, 
        d.Address,
        FooField1 = f == null ? null : f.FooField1, 
        FooField2 = f == null ? null : f.FooField2, 
        BarField1 = b == null ? null : b.BarField1, 
        BarField2 = b == null ? null : b.BarField2
    };

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