Using Linq intersect with sub values?

I found this post Match elements between 2 collections with Linq in c# which explained how you can use Intersect to find matching elements between two lists.

Can you use this to match elements in two lists开发者_运维知识库 that are not of exactly the same, but have "sub values" that you want to match?

My example is this: I have two collections, each containing lists of XElements. The one with elements called <link> and the other with elements called <file>, each have attributes called "path", and it is this attribute I want to match. If the path attribute is equal, I want a match.

In the result set I would like a list of all the elements whose paths match the paths of the elements.

How can this be done?

I would suggest to use LambdaComparer which can be passed into the Intersect() method as Equality Comparer, it allows specifying comparison logic in place by providing boolean condition instead introducing a new comparer class each time, so your code would be clear enough:

firstCollection.Intersect(
              secondCollection, 
              new LambdaComparer<YourClass>(
                  (item1, item2) => item1.PropertyName == item2.PropertyName));


 // Below are lists and User class which demonstrates LambdaComparer and Intersect()
 public class User
 {
      public string Name { get; set; }
 }

 IList<User> list1 = new List<User> 
       { 
          new User {Name = "A"}, 
          new User { Name = "B"}
       };
 List<User> list2 = new List<User> 
      { 
          new User {Name = "C"}, 
          new User { Name = "B"}
      };

 var resultSet = list1.Intersect<User>(
         list2, 
         new LambdaComparer<User>((item1, item2) => item1.Name == item2.Name));

Basically if you need to compare cusotm attributes, you still can encapsulate this logic into

Func<User, User, bool> userNameComparer = (user1, user2) =>
{
 // check attributes using user1.GetType().GetCustomAttributes()
};

And then use this comparer funciton as:

   var resultSet = list1.Intersect<User>(
                     list2, 
                     new LambdaComparer<User>((item1, item2) => userNameComparer));

EDIT: Note ragarding particular impelemntaion referenced in this answer There is could be a problem that by default for hash funciton is hardcoded 0

6  public LambdaComparer(Func<T, T, bool> lambdaComparer) :
7                this(lambdaComparer, o => 0)
8            {
9            }

This can lead to performance issues in some cases so I would recommend to refactor it as:

public LambdaComparer(Func<T, T, bool> lambdaComparer) :
                this(lambdaComparer, 
                      EqualityComparer<T>.Default.GetHashCode(o))
            {
            }

So it wil use built in GetHashCode() implementation