using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var list = new List<Tester>();

        var testerA = new Tester("PHYSICIAN_T");

        var testerB = new Tester("PHYSICIAN_T");

        list.Add(testerA);

        list.Add(testerB);

        Console.WriteLine(string.Format("Are equal? {0}", testerA.Equals(testerB)));

        Console.WriteLine(string.Format("List count? {0}", list.Distinct().Count()));

    }

    public class Tester : IEquatable<Tester> {

        public string EntityType {get;set;}

        public Tester(string entityType) {

            this.EntityType = entityType;   

        }

        // summary 

        // Redefine equality comparer to consider

        // items with the same content as equals.

        // 

        public bool Equals(Tester other)

        {

        //Check whether the compared object is null.

        if (Object.ReferenceEquals(other, null)) return false;

​

        //Check whether the compared object references the same data.

        if (Object.ReferenceEquals(this, other)) return true;

​

        //Check whether the products' properties are equal.

        return EntityType.Equals(other.EntityType);

        }

        public override int GetHashCode()

        {

            return EntityType.GetHashCode();

        }

    }

}