CODEWITHSUNDEEP
c#linqentity-framework
daniel
daniel

Reputation: 35703

LINQ selection and sorting with different relations

I have a DBSet<User> of users. Each User has a DBSet<Activity>of activities. Each activity itself has one or no Category with a name.

public class User
{
    [...]
    DBSet<Activity> activity {get;set;}
}

public class Activity
{
    [...]
    Category category{get;set;}
}

public class Category
{
    [...]
    string Name {get;set;}
}

Now i want to have a List of all users sorted by the number of occurrences of a given category name in activites. In other words: I want a list of users ordered by the number of his activities in a category. How can i do that with LINQ (lambda expressions)?

DBSet<User> users;
string cat="myCategory";
var usersByCategoryActivity = users.OrderByDescending(???);

Upvotes: 1

Views: 92

Answers (3)

Jace Rhea
Jace Rhea

Reputation: 5018

This should work for you:

string cat="myCategory";
DBSet<User> users;
    var usersByCategory = users
             .OrderBy(e=> e.activity.Count(a => a.Categories.Name.Contains(cat)));

Upvotes: 3

Cyril Gandon
Cyril Gandon

Reputation: 17058

Something like that:

DBSet<User> users;
string cat = "myCategory";
var usersByCategoryActivity = users
             .OrderByDescending(u => u.Activities
                            .Where(a => a.Categories.Select(c => c.Name)
                                                    .Contains(cat)
                            .Count()
                     );

If you look inside the query first, it retrieves all the activities which contains the given category. It count it all for a user, and order by that.
I'm not sure this is what you need, but your description is not precise, and there is not a samples of data. So it maybe be good enough. Maybe not.

Upvotes: 1

Jurica Smircic
Jurica Smircic

Reputation: 6445

Maybe

var usersByCategory = users.ToList().OrderBy(e=>e.activity.Count());

Upvotes: 0

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