Getting the same element without changing it using Linq

Question

I have a method like this:

public List<Fruit> Traverse (IEnumerable<Fruit> collection, Action<Fruit> action)

I can do this:

Traverse (array, f => f.Text);

How can I call the action so I get the same element?

Traverse (array, f => f);

C# compiler doesn't allow me to do this.

EDIT:

List<Fruit> result = ...
foreach (Fruit fruit in collection)
{
    result.Add(fruit);
    action(fruit);
}

The method signature is fixed so I can't get anything else by just using an action, right? But what I need is to pass an action that does nothing so I get the whole result list.

Answer 1

Isn't Action a delegate that returns nothing? How about:

Traverse(array, e => {});

Answer 2

Your method declaration doesn't seem right...

If you have this:

public List<string> Traverse (IEnumerable<string> collection, Action<string> action)

You can't be passing in this:

Traverse (array, e => e.Text);

This would require that each element support a "Text" property. String doesn't have a Text property.

If you passed an IEnumerable<string>, then e => e would evaluate to an Func<string, string>. You're returning the string itself.

If you want an Action<string>, you need to do something with the string that doesn't return a value (e).

Answer 3

You've set up your Traverse method wrong. You need to use a generic signature here and a Func<T> return.

public List<T> Traverse (IEnumerable<T> collection, Func<T,T> del)

Answer 4

Action<string> takes a string argument but returns nothing, similar to a method with the signature void Foo(string bar).

If you're using your action parameter to populate the return value than you will need to replace your action with Func<string, string>, which takes a string parameter and returns a string, similar to a function with the signature string Foo(string bar).