Use of "Distinct" method with a custom equality comparer in LINQ

When using the Distinct method in LINQ, you can provide a custom equality comparer to determine uniqueness based on your specific criteria. This allows you to define your own logic for comparing elements and identifying duplicates.

To use the Distinct method with a custom equality comparer, you need to create a class that implements the IEqualityComparer<T> interface, where T is the type of elements in the sequence. This interface defines two methods: Equals and GetHashCode, which are used for comparing elements and generating hash codes respectively.

Here's an example of using the Distinct method with a custom equality comparer:

class Student
{
    public string StdName { get; set; }
    public int StdAge { get; set; }
}

class StudentEqualityComparer : IEqualityComparer<Student>
{
    public bool Equals(Student x, Student y)
    {
        return x.StdName == y.StdName && x.StdAge == y.StdAge;
    }

    public int GetHashCode(Student obj)
    {
        return obj.StdName.GetHashCode() ^ obj.StdAge.GetHashCode();
    }
}

List<Student> people = new List<Student>
{
    new Student { StdName = "Alice", StdAge = 25 },
    new Student { StdName = "Bob", StdAge = 30 },
    new Student { StdName = "Alice", StdAge = 25 }
};

IEnumerable<Student> distinctPeople = people.Distinct(new StudentEqualityComparer());

In this example, the Student class is defined with StdName and StdAge properties. A custom StudentEqualityComparer class is created, implementing the IEqualityComparer<Student> interface. The Equals method is overridden to compare two Student objects based on their StdName and StdAge properties, and the GetHashCode method is implemented to generate a hash code for each Student object.

The Distinct method is then used with the custom equality comparer 'new' StudentEqualityComparer() to remove duplicates from the people collection. The resulting distinctPeople variable will contain the unique Student objects based on the custom equality comparison logic.

By providing a custom equality comparer, you can define your own rules for determining uniqueness when using the Distinct method in LINQ.