Question

I am pretty new to .Net. In classes I have seen objects as IComparer, IEnumerable etc. Could some one explain what does these stand for?

Thanks for your help.

Answer 1

They are interfaces. An interface ensures that an object has certain methods, regardless of it’s class. They are useful when you have code that requires a few common methods, but doesn’t need to know all of the details of the class.

Object(), System.Collections.ArrayList and System.Collections.Queue all implement IEnumerable. If you have a function that asks for an IEnumerable, you can pass an object of any of these classes to the function, and the function is confident that the object implements all of the IEnumerable members.

Try the following code in a console application. These three different classes are all acceptable to pass to PrintAll(items).

Public Sub PrintAll(items As IEnumerable)
    For Each item In items
        Console.WriteLine(item)
    Next
End Sub

Public Sub Main()
    Dim objects As Object() = {1, 2, 3}
    Dim list As New ArrayList({4, 5, 6})
    Dim queue As New Queue({7, 8, 9})
    PrintAll(objects)
    PrintAll(list)
    PrintAll(queue)
    Console.ReadLine()
End Sub