IEnumerable

Question

In this example IEnumerable interface is given a type 'int'. How to explain this situation?. Problem is highlighted.

using System;
using System.Collections.Generic;

class Program
{
static void Main()
{
List<int> oyears = new List<int>();
oyears.Add(1990);
oyears.Add(1991);
oyears.Add(1992);
oyears.Add(1993);
oyears.Add(2001);
oyears.Add(2002);
oyears.Add(2003);

IEnumerable<int> ienum = (IEnumerable<int>)oyears;

foreach (int i in ienum)
{
Console.WriteLine(i);
}

Console.ReadKey();
}
}

Vulpes · Answer

The generic type List implements the generic interface IEnumerable . It therefore follows that List implements IEnumerable and so we can cast the List variable oyears to the IEnumerable type. Moreover we can then assign the result to the variable ienum which is also of the IEnumerable type. In fact you could have done this without a cast since there's always an implicit conversion between a type and an interface which it implements. So this would also work just as well: using System; using System.Collections.Generic; class Program { static void Main() { List oyears = new List (); oyears.Add(1990); oyears.Add(1991); oyears.Add(1992); oyears.Add(1993); oyears.Add(2001); oyears.Add(2002); oyears.Add(2003); IEnumerable ienum = oyears; foreach (int i in ienum) { Console.WriteLine(i); } Console.ReadKey(); } }

Maha · Answer

Thank you for your explanation.