Applying automatic and hidden filtering to a List<T>

OK.

I have a class MyClass an开发者_StackOverflow社区d another class that is based on List. Let's call it MyCollection.

Now when someone types:

MyCollection coll = new MyCollection();
...
coll.Find(...)

They are acting on the entire collection. I want to apply some filtering - behind the scenes - so that if they write the above code, what actually executes is something like...

coll.Where(x=>x.CanSeeThis).Find(...)

What do I need to write in the definition of the MyCollection class to make this work?

Can I make this work?

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You probably want to write a wrapper class that implements IList or ICollection, using a regular List internally. This wrapper class would then proxy all method calls to the internal list, applying the filter as required.

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You´ve already mentioned you´ve got your own collection, probably derived from List right? Then you´ll need to create your own method for finding:

public class MyList<T> : System.Collections.Generic.List<T>
{
  public IEnumerable<T> MyFind(Predicate<T> match)
  {
    return this.Where(x => x.CanSeeThis).ToList().Find(match);
  }
}

This unfortunatly is needed because you cannot override the Find method on List directly. You can however use the 'new' keyword to specify that If you´ve got a reference to the instance of MyList it will use that implementation of find, like below:

  public new IEnumerable<T> Find(Predicate<T> match)
  {
    return this.Where(x => x.CanSeeThis).ToList().Find(match);
  }

However the above example will yield:

MyCollection<int> collection = new ...
collection.Find(myPredicate); // <= Will use YOUR Find-method

List<int> baseTypeCollection = collection; // The above instantiated
baseTypeCollection.Find(myPredicate); // Will use List<T>.Find!

So it´s better you make you´re own method.