Question

I just want to bind one collection to another one:
Lets say there is a

List<string> original = new List<string>();

and there is a

List<string> extended = 
           new List<string>(from curItem in originals select curItem + "_extension");

So the items of the extended are just the same than the original’s but with an “_extension” at the end.

What I want is to bind the extended to the original, so that if the original becomes changed, the extended also changes.

I know I could use events and recreate the extended every time.
But I think this is not efficient.

Edit:
Lets say: original is large and it is too exhausting to recreate the single elements of the extended and its also exhausting to create a single element at all.
So I want to have two lists (or collections) where on observes the other one and adds or removes the changes, like the data binding in Wpf, but adding an extension.

Answer 1

You can use the BindingList<T> class on System.ComponentModel to achieve this… maybe it’s like killing a fly with a hammer, but will serve to more complex examples.

I think you can make an extension method like this:

static class ExtensionMethods
{
    public static IEnumerable<string> Extensions(this IEnumerable<string> strs)
    {
        foreach (var str in strs)
        {
            yield return str + "_extension";
        }
    }
}

And you can use this on every IEnumerable<String>:

foreach (var x in original.Extensions())
{
    Console.WriteLine(x);
}