Why is it important to override the GetHashCode method in classes?

Overriding the GetHashCode method is important for the correct functioning of objects in hash-based collections such as Dictionary, HashSet, and others.

Reasons:

• GetHashCode returns a numeric value used for quick object lookup in hash tables.
• If two objects are considered equal (by the Equals method), they should return the same hash code so that collections handle them correctly.
• If GetHashCode is not overridden along with Equals, objects may be compared incorrectly or duplicated in collections.

Example:

class Person
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override bool Equals(object obj)
    {
        if (obj is Person other)
            return Name == other.Name && Age == other.Age;
        return false;
    }

    public override int GetHashCode()
    {
        return HashCode.Combine(Name, Age);
    }
}

Thus, overriding GetHashCode ensures consistency with Equals and proper functioning of objects in hash structures.