Question

How do I go from (cast?, convert?):

IEnumerable<Square>

to

IEnumerable<Shape>

Answer 1

If you’re using anything lower than .NET 4.0, then you’re going to have to use IEnumerable.Cast:

IEnumerable<Square> squares = new List<Square>();

// Fill the collection

IEnumerable<Shape> shapes = squares.Cast<Shape>();

.NET 4.0 introduces new Covariance and Contravariance features that allow you to make that cast directly:

IEnumerable<Square> squares = new List<Square>();
IEnumerable<Shape> shapes = (IEnumerable<Shape>)squares;