如何合并两个列表 [英] How to Merge two lists
问题描述
我想合并以下课程的两个列表
I want to merge two list of the following class
public class ContactsByUser
{
public int UserId { get; set; }
public string Username { get; set; }
public int CountContacts { get; set; }
public int CountBehaviorInterview { get; set; }
public override bool Equals(object obj)
{
return this.UserId == ((ContactsByUser)obj).UserId;
}
public override int GetHashCode()
{
return UserId.GetHashCode();
}
}
现在我有2个包含以下内容的列表
Now I have 2 lists containing the following
List<ContactsByUser> contacts = new List<ContactsByUser>();
contacts.Add( new ContactsByUser { UserId = 1, Username = user1, CountContacts = 42, CountBehaviorInterview = 0});
contacts.Add( new ContactsByUser { UserId = 2, Username = user2, CountContacts = 25, CountBehaviorInterview = 0});
contacts.Add( new ContactsByUser { UserId = 3, Username = user3, CountContacts = 7, CountBehaviorInterview = 0});
contacts.Add( new ContactsByUser { UserId = 4, Username = user4, CountContacts = 10, CountBehaviorInterview = 0});
contacts.Add( new ContactsByUser { UserId = 5, Username = user5, CountContacts = 23, CountBehaviorInterview = 0});
contacts.Add( new ContactsByUser { UserId = 6, Username = user6, CountContacts = 60, CountBehaviorInterview = 0});
contacts.Add( new ContactsByUser { UserId = 7, Username = user7, CountContacts = 3, CountBehaviorInterview = 0});
List<ContactsByUser> interviews = new List<ContactsByUser>();
interviews .Add( new ContactsByUser { UserId = 1, Username = user1, CountContacts = 0, CountBehaviorInterview = 33});
interviews .Add( new ContactsByUser { UserId = 2, Username = user2, CountContacts = 0, CountBehaviorInterview = 21});
interviews .Add( new ContactsByUser { UserId = 3, Username = user3, CountContacts = 0, CountBehaviorInterview = 8});
interviews .Add( new ContactsByUser { UserId = 4, Username = user4, CountContacts = 0, CountBehaviorInterview = 17});
合并这两个列表后,我希望得到的结果如下
What I would like to have when I merge these 2 lists is the following result
{ UserId = 1, Username = user1, CountContacts = 42, CountBehaviorInterview = 33});
{ UserId = 2, Username = user2, CountContacts = 25, CountBehaviorInterview = 21});
{ UserId = 3, Username = user3, CountContacts = 7, CountBehaviorInterview = 8});
{ UserId = 4, Username = user4, CountContacts = 10, CountBehaviorInterview = 17});
{ UserId = 5, Username = user5, CountContacts = 23, CountBehaviorInterview = 0});
{ UserId = 6, Username = user6, CountContacts = 60, CountBehaviorInterview = 0});
{ UserId = 7, Username = user7, CountContacts = 3, CountBehaviorInterview = 0});
在第一个列表上,CountBehaviorInterview属性将始终为0,在第二个列表上,CountContacts将始终为0.
On the first list, the CountBehaviorInterview property will always be 0, and on the second list the CountContacts will always be 0.
我尝试使用union,但它所做的只是返回一个列表,其中包含2个列表.有没有一种方法可以按照我的需要进行合并?
I have tried using union but all it does is return a list with the 2 lists inside. Is there a way merge these the way i need?
推荐答案
如果可以更改contacts
列表中的对象,可以在foreach
中使用简单的Join
:
If you're fine with changing the objects in the contacts
list, you could use a simple Join
with foreach
:
foreach(var joined in contacts.Join(interviews,
o => o.UserId,
i => i.UserId,
(originalContact, i) => new {originalContact, i.CountBehaviorInterview}))
{
joined.originalContact.CountBehaviorInterview = joined.CountBehaviorInterview;
}
如果要创建ContactsByUser
的新实例,那么您正在寻找左外部联接,如下所示:
If you want to create new instances of ContactsByUser
, then you're looking for a left outer join, something like this:
var result = from i in contacts
join o in interviews on i.UserId equals o.UserId into j
from o in j.DefaultIfEmpty()
select new ContactsByUser
{
UserId = i.UserId,
Username = i.Username,
CountContacts = i.CountContacts,
CountBehaviorInterview = j.Any() ? j.Single().CountBehaviorInterview : 0
};
或者,使用其他方法(可能会更慢,具体取决于您的数据,但可能没有关系):
or, using a different method (may be slower, depending on your data, but probably doesn't matter):
var result = from i in contacts
from o in interviews.Where(k => k.UserId == i.UserId).DefaultIfEmpty()
select new ContactsByUser
{
UserId = i.UserId,
Username = i.Username,
CountContacts = i.CountContacts,
CountBehaviorInterview = o != null ? o.CountBehaviorInterview : 0
};
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