using System;

// this is the delegate declaration
public delegate int Comparer(object obj1, object obj2);

public class Name
{
    public string FirstName = null;
    public string LastName = null;

    public Name(string first, string last)
    {
        FirstName = first;
        LastName = last;
    }

    // this is the delegate method handler
    public static int CompareFirstNames(object name1, object name2)
    {
        string n1 = ((Name)name1).FirstName;
        string n2 = ((Name)name2).FirstName;

        if (String.Compare(n1, n2) > 0)
        {
            return 1;
        }
        else if (String.Compare(n1, n2) < 0)
        {
            return -1;
        }
        else
        {
            return 0;
        }
    }

    public override string ToString()
    {
        return FirstName + " " + LastName;
    }
}

class SimpleDelegate
{
    Name[] names = new Name[5];

    public SimpleDelegate()
    {
        names[0] = new Name("Joe", "Mayo");
        names[1] = new Name("John", "Hancock");
        names[2] = new Name("Jane", "Doe");
        names[3] = new Name("John", "Doe");
        names[4] = new Name("Jack", "Smith");
    }

    static void Main(string[] args)
    {
        SimpleDelegate sd = new SimpleDelegate();

        // this is the delegate instantiation
        Comparer cmp = new Comparer(Name.CompareFirstNames);

        Console.WriteLine("\nBefore Sort: \n");

        sd.PrintNames();

        // observe the delegate argument
        sd.Sort(cmp);

        Console.WriteLine("\nAfter Sort: \n");

        sd.PrintNames();
    }

    // observe  the delegate parameter
    public void Sort(Comparer compare)
    {
        object temp;

        for (int i=0; i < names.Length; i++)
        {
            for (int j=i; j < names.Length; j++)
            {
                // using delegate "compare" just like
                // a normal method
                if ( compare(names[i], names[j]) > 0 )
                {
                    temp = names[i];
                    names[i] = names[j];
                    names[j] = (Name)temp;
                }
            }
        }
    }

    public void PrintNames()
    {
        Console.WriteLine("Names: \n");

        foreach (Name name in names)
        {
            Console.WriteLine(name.ToString());
        }
    }
}