如何使用Distinct从Linq查询中选择特定对象？

Question

I have a list with two or more objects of class Agent.

Name = "A"

Priority = 0

ResultCount = 100

;

Name = "B"

Priority = 1

ResultCount = 100

;

Both objects have the same ResultCount. In that case I only need one object and not two or more. I did this with a Linq Query with Distinct and an custom made Comparer.

IEnumerable<Agent> distinctResultsAgents = 
(from agt in distinctUrlsAgents select agt).Distinct(comparerResultsCount);

With this query I get only one object from the list but I never know which one. But I don't want just any object, I want object "B" because the Priority is higher then object "A". How can I do that?

My custom Comparer is very simple and has a method like this:

    public bool Equals(Agent x, Agent y)
    {
        if (x == null || y == null)
            return false;

        if (x.ResultCount == y.ResultCount)
            return true;

        return false;
    } 

Answer 1

First group the elements by ResultCount so that you only get one result for each distinct value of ResultCount . Then for each group select the element in that group with the highest priority.

Try this query:

IEnumerable<Agent> distinctResultsAgents =
    from d in distinctUrlsAgents
    group d by d.ResultCount into g
    select g.OrderByDescending(x => x.Priority).First();

If you use morelinq there is a function called MaxBy that you could use instead of the last line, but note that it only works for LINQ To Objects.