Convert CollectionBase to List or data type usable with Linq

.net, c#, ienumerable, ienumerator, linq

Solution

Just use the `Enumerable.Cast<T>()` extension method on the non-generic `IEnumerable` interface, which you can do implicitly in a query expression:

var query = from Picture picture in pictures
            where ...
            select ...;

or explicitly, for instance if you want to use dot notation:

var query = pictures.Cast<Picture>()
                    .Where(...)
                    .Select(...);

An alternative to `Cast<T>()` is `OfType<T>()` - which basically ignores any elements which aren't of the right type. In this case I think `Cast<T>()` is more appropriate though.

If you want to convert the whole collection to a `List<T>` for whatever reason, that's easy too:

List<Picture> list = pictures.Cast<Picture>().ToList();

Problem

I am using Aspose cells to manipulate Excel spreadsheets. One of the types in the API is a collection of Pictures in the spreadsheet, which derives from CollectionBase: see this link: http://www.aspose.com/documentation/.net-components/aspose.cells-for-.net/aspose.cells.pictures.html I want to convert this type to something that allows me to use Linq expressions What are the options for this? I guess I could iterate over it and manually add it to a `new List<Picture>` But is there a better way to do this? I have read this question Adding IEnumerable<T> to class derived from CollectionBase But I obviously don't have control over the class that implements CollectionBace as it is a third party product

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