sasan-salem

class Student : IComparable<Student>
{
    public string Name { get; set; }
    public int Number { get; set; }
    public int SerialNo { get; set; }
    public int Grade { get; set; }

    public int CompareTo(Student other)
    {
        if (other.SerialNo < SerialNo)

sasan-salem

class SerialNoComparer : IComparer<Student>
{
    public int Compare(Student s1, Student s2)
    {
        return s1.SerialNo.CompareTo(s2.SerialNo);
    }
}

sasan-salem

class Student
{
    public string Name { get; set; }
    public int Number { get; set; }
    public int SerialNo { get; set; }
    public int Grade { get; set; }

    public static IEqualityComparer<Student> SerialNoComparer { get => new SerialNoEqualityComparer(); }
    public static IEqualityComparer<Student> NumberComparer { get => new NumberEqualityComparer(); }

sasan-salem

List<Student> students = new List<Student>();
// Add some students to this List
var specificStudent = new Student() { SerialNo = 12, Number = 34, Grade = 3, Name = "Joe" };
bool exist1 = students.Contains(specificStudent, new NumberEqualityComparer());
bool exist2 = students.Contains(specificStudent, new SerialNoEqualityComparer());

sasan-salem

  class NumberEqualityComparer : IEqualityComparer<Student>
  {
      public bool Equals(Student s1, Student s2)
      {
          if (s1 == null && s2 == null)
              return true;
          else if (s1 == null || s2 == null)
              return false;
          else if (s1.Number == s2.Number)
              return true;

sasan-salem

class SerialNoEqualityComparer : IEqualityComparer<Student>
  {
      public bool Equals(Student s1, Student s2)
      {
          if (s1 == null && s2 == null)
              return true;
          else if (s1 == null || s2 == null)
              return false;
          else if (s1.SerialNo == s2.SerialNo)
              return true;

sasan-salem

class Student : IEquatable<Student>
{
    public string Name { get; set; }
    public int Number { get; set; }
    public int SerialNo { get; set; }
    public int Grade { get; set; }

    public bool Equals(Student other)
    {
        if (other.SerialNo == SerialNo)

sasan-salem

class Student : IEquatable<Student>
{
    public string Name { get; set; }
    public int Number { get; set; }
    public int SerialNo { get; set; }
    public int Grade { get; set; }

    public bool Equals(Student other)
    {
        if (other.SerialNo == SerialNo)

sasan-salem

bool result = false;
if (student1.GetHashCode() == student2.GetHashCode())
        result = student1.Equals(student2);

sasan-salem

Student student1 = new Student()
{
    Name = "Joe",
    Grade = 3,
    Number = 10,
    SerialNo = 3213214
};

Student student2 = new Student()
{