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How to convert a LINQ expression with a few "from" from query syntax to method syntax?

Iam using the Entity Framework. How to write the following Linq code in Lambda C #?

var users = (from u in context.Users.ToList()
                         from e in u.Events
                         where e.EventName == eventName //Name of the Event, the user is related to
                         select u.FirstName + u.LastName).ToList();

It is impossible to get through Lambda in this situation.

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3 answers

The equivalent in the “Method Chain” (what he called) is as follows:

context.Users.SelectMany(u => u.Events
                               .Where(e => e.EventName == eventName)
                               .Select(e => u.FirstName + u.LastName))
             .ToList();

Please note that I dropped the call ToList()on context.Usersbecause it seems unnecessary.

+2
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context.Users.SelectMany(u => u.Events.Where(e => e.EventName == eventName).
                                       Select(e => u.FirstName + u.LastName)).
              ToList();
+3
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var users = context.Users
            .Where(u => u.Events.Any(q => q.EventName == eventName))
            .Select(m => m.FirstName + m.LastName).ToList();

, ;

public class User
{
    public List<Event> Events { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class Event
{
    public string EventName { get; set; }
}

;

string eventName = "a";

List<User> t = new List<User>();

Event event1 = new Event() { EventName = "a" };
Event event2 = new Event() { EventName = "b" };
Event event3 = new Event() { EventName = "c" };

User user1 = new User() { FirstName = "x", LastName = "y" };
User user2 = new User() { FirstName = "x1", LastName = "y1" };
User user3 = new User() { FirstName = "x2", LastName = "y2" };

user1.Events = new List<Event>();
user2.Events = new List<Event>();
user3.Events = new List<Event>();

user1.Events.Add(event1);
user1.Events.Add(event2);

user2.Events.Add(event2);
user2.Events.Add(event3);

user3.Events.Add(event1);
user3.Events.Add(event3);

t.Add(user1);
t.Add(user2);
t.Add(user3);

var bb = t.Where(u => u.Events.Any(q => q.EventName == eventName)).Select(m => m.FirstName + m.LastName).ToList();
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