C# 使用 Linq 从嵌套集合中选择对象
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Select object from nested collection using Linq
提问by w3dev
I have a class structure something like this:
我有一个类似这样的类结构：
class MyClass
{
public IEnumerable<AttributeGroup> AttributeGroups { get; set; }
}
class AttributeGroup
{
public IEnumerable<Attribute> Attributes { get; set; }
}
class Attribute
{
public string SomeProp { get; set; }
}
I need to get all 'Attributes' which has a specific 'SomeProp' value no matter which Attribute Group they belong to.
我需要获取所有具有特定“SomeProp”值的“属性”，无论它们属于哪个属性组。
For example, SomeProperty== 'A'can be found in both MyClassObj.AttributeGroup[0]and MyClassObj.AttributeGroup[5]and I need to write a Linq (or something like that) to fetch two objects from these two different attributegroups.
例如，SomeProperty== 'A'可以在MyClassObj.AttributeGroup[0]and 中找到，MyClassObj.AttributeGroup[5]我需要编写一个 Linq（或类似的东西）来从这两个不同的属性组中获取两个对象。
Any suggestion?
有什么建议吗？
采纳答案by JustAnotherUserYouMayKnow
First select all attributes from all attribute groups, then only select the ones with your property.
首先从所有属性组中选择所有属性，然后仅选择具有您的属性的属性。
IEnumerable<Attribute> attributes =
myClassInstance
.AttributeGroups
.SelectMany(x => x.Attributes)
.Where(x => x.SomeProperty == 'A');
Other Linq-style syntax:
其他 Linq 风格的语法：
IEnumerable<Attribute> attributes =
from attributeGroup in myClassInstance.AttributeGroups
from attribute in attributeGroup.Attributes
where attribute.SomeProperty == 'A'
select attribute;
回答by Marcelo Cantos
Your example isn't clear; I can't tell what you mean by, "two object from these two different attributegroups". I'll guess that you want the groups that have attributes with the property in question:
你的例子不清楚；我不知道你说的“来自这两个不同属性组的两个对象”是什么意思。我猜您想要具有相关属性的属性的组：
from g in MyClassObj.AttributeGroups
where g.Any(attr => attr.SomeProperty == "A")
select g
回答by Andreas Schlapsi
Have a look at SelectMany (http://msdn.microsoft.com/en-us/library/bb534336.aspx).
看看 SelectMany ( http://msdn.microsoft.com/en-us/library/bb534336.aspx)。
For example:
例如：
myClassObjs.SelectMany(o => o.AttributeGroups.SelectMany(g => g.Attributes)).Where(a => a.SomeProp == "A")
This line selects all Attribute objects of all AttributeGroups of all MyClass objects where SomeProp equals "A". a in the lambda expression for Where is of type Attribute.
此行选择所有 MyClass 对象的所有 AttributeGroups 的所有 Attribute 对象，其中 SomeProp 等于“A”。Where 的 lambda 表达式中的 a 是 Attribute 类型。
