Why C# LINQ Distinct() doesn’t work?

Question

Aryan Kumar · Answer

The Distinct() method in LINQ is used to remove duplicates from a sequence. The
Distinct() method takes an optional parameter that specifies the comparer to use when comparing elements. If the parameter is 0, the default comparer is used. The default comparer compares elements by their GetHashCode() method.
The GetHashCode() method returns a hash code for an object. The hash code is used to quickly compare elements in a hash table. However, the GetHashCode() method does not guarantee that two objects with different values will have different hash codes. This is why the Distinct() method with a parameter of 0 does not work.
To use the Distinct() method to remove duplicates, you need to specify a comparer that guarantees that two objects with different values will have different hash codes. You can use the
IEqualityComparer interface to create a custom comparer.
The following code is an example of how to use the Distinct() method with a custom comparer:
C#
public class Person {
    public string Name { get; set; }
}
public class PersonComparer : IEqualityComparerandlt;Person> {
    public bool Equals(Person x, Person y) {
        return x.Name == y.Name;
    }
    public int GetHashCode(Person obj) {
        return obj.Name.GetHashCode();
    }
}
var people = new Listandlt;Person>();
people.Add(new Person { Name = "John" });
people.Add(new Person { Name = "Jane" });
people.Add(new Person { Name = "John" });
var distinctPeople = people.Distinct(new PersonComparer());
In this code, the PersonComparer class implements the IEqualityComparer interface and provides a custom comparer for the
Person class. The Equals() method compares the names of two
Person objects and returns a value indicating whether the two objects are equal. The
GetHashCode() method returns a hash code for a Person object.
The distinctPeople variable is a list that contains only the distinct
Person objects from the people list.

forum

Why C# LINQ Distinct() doesn’t work?

Sandra Emily

Can you answer this question?

1 Answers

Liked By