using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Foo foo = new Foo()

        {Id = 1, Name = "test"};

        Console.WriteLine("foo ToString = " + foo.ToString());

        List<Foo> list = new List<Foo>();

        for (int i = 0; i < 10; i++)

        {

            list.Add(new Foo{Id = i, Name = "foo " + i});

        }

​

        Console.WriteLine("list ToString = " + list.ToCustomString());

    }

}

​

// Moved Foo out to global scope so the extension method could 

// resolve it and the extension class needed to be in global scope.

public class Foo

{

    public int Id

    {

        get;

        set;

    }

​

    public string Name

    {

        get;

        set;

    }

​

    public override string ToString()

    {

        string output = "\r\n";

        output += "Id:" + this.Id.ToString() + "\r\n";

        output += "Name: " + this.Name + "\r\n";

        return output;

    }

}

​

public static class MyListOfFoosExtensions

{

    public static string ToCustomString(this IEnumerable<object> list)

    {

        string output = "\r\n";

        foreach (var el in list)

        {

            output += el.ToString() + "\r\n";

        }

​

        return output;

    }

}/*

public static class FooExtensions

{

    public static string ToString<T>(this T obj)

        where T : Foo

    {

        string output = "\r\n";

        output += "Id:" + obj.Id.ToString() + "\r\n";

        output += "Name: " + obj.Name + "\r\n";

        return output;

    }

}

​

public static class MyListOfFoosExtensions

{ 

    public static string ToString<T>(this List<T> list)

        where T : Foo

    {

        string output = "\r\n";

        foreach (var el in list)

        {

            output += el.ToString<T>() + "\r\n";    

        }

        return output;

    } 

}

*/

​