Cédric Bourgeois Cédric Bourgeois - 1 year ago 72
C# Question

ivalueconverter vs system.converter vs delegate

I'm implementing a ConvertingCollection, which aims to provide a collection of converted items (B), given a live collection of original items (A). The Collection B would reflect any change occurring in Collection A. The target is to use it in MVVM as a collection of ViewModels given a collection of Models, but I believe that it could be used in many different contexts.

This class requires the user to provide a way to convert objects from a type A to a type B. I can find several ways to proceed, but I don't know enough about their differences to decide what is the best approach :

  • I could ask for an
    , which seems to be WPF-related. Now, nothing prevents to use it elsewhere, but it might be confusing. Although my class is first intended to be used in a WPF context, it is generic enough to apply to many other contexts. In addition, the
    converts from object to object, which means casting downstream, and no crash at build time.

  • I could opt for a
    . This allows the usage of
    and, even more pleasant, I can ask for specific types. Plus, this is not WPF-related in people's mind, as far as I know.

  • Finally, I could just go with a delegate doing TypeIn => TypeOut. No class to be instanciated, strongly typed, and the user could use any of IValueConverter, Converter or custom function to implement the delegate.

Now, I have no idea why the
exist when everything could be handled with just delegates. So I guess I'm missing something there.

Can anyone please help ?
Thanks in advance,
Best regards

Answer Source

The best approach according to me:

  • Let the user decide whether to use IValueConverter or Converter by implementing a class that offers both possibilities.
  • The lambda is out of scope because a lambda expression is what is used on the user side to easily provide a delegate implementation. This means that a ConvertingCollection would expect a delegate as parameter, which is what a Converter already is.
  • Finally, the idea to use an implicit conversion is not kept because :
    • It forces the user to provide a conversion that could apply anywhere and not only in the sole context of the usage of ConvertingCollection, which may be problematic sometimes
    • In case an implicit conversion applies, is is easy to use it in a lambda expression
    • It makes the implementation of the ConvertingCollection more complex (check if an implicit conversion exists between the 2 types A and B), and I'm too lazy for this. Ok, that may be the first reason, but the other two are still valid. :)

I hope this helps.

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download