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Start your free trialchazber
4,873 PointsFeeding HashSet constructor a List with duplicate item not automatically removing it.
using System;
using System.Collections.Generic;
namespace Treehouse
{
class Program
{
static void Main()
{
List<Student> pre =new List<Student>
{
new Student() { Name = "Sally", GradeLevel = 3 },
new Student() { Name = "Bob", GradeLevel = 3 },
new Student() { Name = "Sally", GradeLevel = 2 },
new Student() { Name = "Sally", GradeLevel = 2 }
};
HashSet<Student> students = new HashSet<Student>(pre);
SchoolRoll schoolRoll = new SchoolRoll();
schoolRoll.AddStudents(students);
foreach(Student student in schoolRoll.Students)
{
Console.WriteLine($"{student.Name} is in grade {student.GradeLevel}");
}
}
}
}
Anybody know why?
2 Answers
Steven Parker
231,198 PointsA new instance of a HashSet<T> class uses the default equality comparer for the set type. The definition of "Student" is not shown here, but my first guess would be that it needs a comparer that will judge equality using the contents.
chazber
4,873 PointsThanks Steve. I should've just waited to watch the next vids :)