Distinct not working with LINQ to Objects

Question

class Program
{
    static void Main(string[] args)
    {
        List books = new List 
        {
            new Book
            {
                


        

Answer 1

Distinct() performs the default equality comparison on objects in the enumerable. If you have not overridden Equals() and GetHashCode(), then it uses the default implementation on object, which compares references.

The simple solution is to add a correct implementation of Equals() and GetHashCode() to all classes which participate in the object graph you are comparing (ie Book and Author).

The IEqualityComparer interface is a convenience that allows you to implement Equals() and GetHashCode() in a separate class when you don't have access to the internals of the classes you need to compare, or if you are using a different method of comparison.