How-To: "Cast" between List<T>'s

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How-To: "Cast" between List<T>'s

published 1 year, 6 months ago, submitted by dwhittaker 1 year, 6 months ago

devlicio.us — If you've ever tried to cast been list generics, you know that you can't.

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tags: List, Cast, Generics, Collections | tag it

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Comments:

I find using a generic method for this a lot easier:

public IEnumerable<TBase> As<TBase, TDerived>(IEnumerable<TDerived> derived)
where TDerived : TBase
{
foreach(TDerived item in derived) yield return item;
}

You call it like this:

// C# 2
IEnumerable<Square> mySquares = ...;
IEnumerable<Shape> myShapes = As<Shape, Square>(mySquares);

// C# 3 with extension methods would make it a little more natural:
IEnumerable<Shape> myShapes = mySquares.As<Shape>();

posted by

JudahGabriel 1 year, 6 months ago

Oh, and if you need to create a list from that, it's as simple as saying

List<Shape> shapes = new List<Shape>(myShapes);

posted by

JudahGabriel 1 year, 6 months ago