How Can I Group Person Objects by PersonID and Get Unique Car Models Using LINQ?

Use linq to group Personid

In this example, your goal is to group the Person object list according to the Personid attribute and retrieve the only car model list for everyone. To this end, you can use the Groupby extension provided by Linq.

The following linq query demonstrates how to group the Personid and extract the car list associated with everyone:

var results = from p in persons
              group p.car by p.PersonId into g
              select new { PersonId = g.Key, Cars = g.Distinct().ToList() };

Explanation:

Create all CAR attributes based on each unique Personid value.

• The result of the grouping is the sequence of anonymous objects. Each object represents a group and contains Personid as the key and car list as the CARS attribute. group p.car by p.PersonId Methods ensure that only the only car model is returned.
• Distinct() or, you can use lookup to effectively retrieve the car list of specific Personid:

Usage:

var carsByPersonId = persons.ToLookup(p => p.PersonId, p => p.car);

If there is no designated person ID in this method, a empty sequence is returned. Make sure to return the only car model list.

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