Question

I wonder what’s the pros/cons of using delegate vs OOP when implementing strategy design pattern?

Which one do you recommend to use? or what kind of problem does delegate solve? and why should we use OOP if OOP is better?

Thanks!

-tep

Answer 1

Both techniques can be powerful and valuable – here are some of my opinions about when to use which.

Use an Interface/Implementation approach when the strategy:

2. maintains state
3. needs configuration
4. uses dependency injection
5. needs to be configured by an IoC container (think ConnectionProvider)
6. combines multiple responsibilities (think DataAdapter from ADO.NET)
7. is too complex or long as a single method
8. is likely to be subclassed to create new strategies
9. needs to return state information to the caller
10. needs to access internals of the object is applies to
11. Would require too many direct parameters

Otherwise, tend to use delegates based on Func<> or Action<>, especially if

1. There are likely to be a very large variety of strategies (think sort expressions)
2. The strategy is best expressed as as lambda
3. There’s an existing method you want to leverage