C# Language Equals and GetHashCode Override Equals and GetHashCode on custom types
Example
For a class Person like:
public class Person
{
public string Name { get; set; }
public int Age { get; set; }
public string Clothes { get; set; }
}
var person1 = new Person { Name = "Jon", Age = 20, Clothes = "some clothes" };
var person2 = new Person { Name = "Jon", Age = 20, Clothes = "some other clothes" };
bool result = person1.Equals(person2); //false because it's reference Equals
But defining Equals and GetHashCode as follows:
public class Person
{
public string Name { get; set; }
public int Age { get; set; }
public string Clothes { get; set; }
public override bool Equals(object obj)
{
var person = obj as Person;
if(person == null) return false;
return Name == person.Name && Age == person.Age; //the clothes are not important when comparing two persons
}
public override int GetHashCode()
{
return Name.GetHashCode()*Age;
}
}
var person1 = new Person { Name = "Jon", Age = 20, Clothes = "some clothes" };
var person2 = new Person { Name = "Jon", Age = 20, Clothes = "some other clothes" };
bool result = person1.Equals(person2); // result is true
Also using LINQ to make different queries on persons will check both Equals and GetHashCode:
var persons = new List<Person>
{
new Person{ Name = "Jon", Age = 20, Clothes = "some clothes"},
new Person{ Name = "Dave", Age = 20, Clothes = "some other clothes"},
new Person{ Name = "Jon", Age = 20, Clothes = ""}
};
var distinctPersons = persons.Distinct().ToList();//distinctPersons has Count = 2
