Distinct() with lambda?

Question

Right, so I have an enumerable and wish to get distinct values from it.

Using System.Linq, there\'s of course an extension method called Distinct<

Answer 1

IEnumerable lambda extension:

public static class ListExtensions
{        
    public static IEnumerable Distinct(this IEnumerable list, Func hashCode)
    {
        Dictionary hashCodeDic = new Dictionary();

        list.ToList().ForEach(t => 
            {   
                var key = hashCode(t);
                if (!hashCodeDic.ContainsKey(key))
                    hashCodeDic.Add(key, t);
            });

        return hashCodeDic.Select(kvp => kvp.Value);
    }
}

Usage:

class Employee
{
    public string Name { get; set; }
    public int EmployeeID { get; set; }
}

//Add 5 employees to List
List lst = new List();

Employee e = new Employee { Name = "Shantanu", EmployeeID = 123456 };
lst.Add(e);
lst.Add(e);

Employee e1 = new Employee { Name = "Adam Warren", EmployeeID = 823456 };
lst.Add(e1);
//Add a space in the Name
Employee e2 = new Employee { Name = "Adam  Warren", EmployeeID = 823456 };
lst.Add(e2);
//Name is different case
Employee e3 = new Employee { Name = "adam warren", EmployeeID = 823456 };
lst.Add(e3);            

//Distinct (without IEqalityComparer) - Returns 4 employees
var lstDistinct1 = lst.Distinct();

//Lambda Extension - Return 2 employees
var lstDistinct = lst.Distinct(employee => employee.EmployeeID.GetHashCode() ^ employee.Name.ToUpper().Replace(" ", "").GetHashCode());