Overridding Equals and GetHash

Question

I have read that when you override Equals on an class/object you need to override GetHashCode.

 public class Person : IEquatable
    {
                 


        

Answer 1

Here is how I would do it. Since it is common for two different people to have exactly the same name it makes more sense to use a unique identifier (which you already have).

public class Person : IEquatable
{
  public override int GetHashCode()
  {
    return PersonId.GetHashCode();
  }

  public override bool Equals(object obj)
  {
    var that = obj as Person;
    if (that != null)
    {
      return Equals(that);
    }
    return false;
  }

  public bool Equals(Person that)
  {
    return this.PersonId == that.PersonId;
  }
}

To answer your specific question: This only matters if you are using Person as a key in an IDictionary collection. For example, Dictionary or SortedDictionary, but not Dictionary.