鲜明的Linq在一个特定的属性 [英] Linq Distinct on a particular Property
问题描述
我玩的LINQ学习一下吧,但我不知道如何使用DISTINCT时,我没有一个简单的列表(整数一个简单的列表是pretty的容易做到的,这并不是题)。如果想使用分明
对象对对象的一个或多个属性的列表上?
I am playing with Linq to learn about it but I can't figure out how to use Distinct when I do not have a simple list (a simple list of integers is pretty easy to do, this is not the question). What if want to use Distinct
on a list of an Object on ONE or MORE Properties of the object?
例如:如果一个对象是人
,与地产编号
。我怎样才能让所有的人,并使用分明
它们与对象的属性编号
?
Example: If an object is Person
, with Property Id
. How can I get all Person and use Distinct
on them with the property Id
of the object?
Person1: Id=1, Name="Test1"
Person2: Id=1, Name="Test1"
Person3: Id=2, Name="Test2"
我怎样才能得到公正PERSON1和Person3?那可能吗?
How can I get just Person1 and Person3? Is that possible?
如果这是不可能的使用LINQ,这将是有人
取决于它的一些属性在.NET 3.5中的列表最好的方法是什么?
If it's not possible with Linq, what would be the best way to have a list of Person
depending on some of its Properties in .Net 3.5?
推荐答案
修改:这是现在 MoreLINQ部分。
您需要的是一个明显的,通过有效。我不相信这是LINQ的一部分,因为它的立场,虽然它很容易写:
What you need is a "distinct-by" effectively. I don't believe it's part of LINQ as it stands, although it's fairly easy to write:
public static IEnumerable<TSource> DistinctBy<TSource, TKey>
(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
HashSet<TKey> seenKeys = new HashSet<TKey>();
foreach (TSource element in source)
{
if (seenKeys.Add(keySelector(element)))
{
yield return element;
}
}
}
因此,要找到只使用了编号
属性不同的值,你可以使用:
So to find the distinct values using just the Id
property, you could use:
var query = people.DistinctBy(p => p.Id);
和使用多个属性,你可以使用匿名类型,适当地实现平等的:
And to use multiple properties, you can use anonymous types, which implement equality appropriately:
var query = people.DistinctBy(p => new { p.Id, p.Name });
未经检验的,但它应该工作(现在它至少编译)。
Untested, but it should work (and it now at least compiles).
它假定默认的比较的钥匙,但 - 如果你想传递一个相等比较,只是把它传递给了的HashSet
构造
It assumes the default comparer for the keys though - if you want to pass in an equality comparer, just pass it on to the HashSet
constructor.
这篇关于鲜明的Linq在一个特定的属性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!