Invoking methods based on a parameter without if-else statements in C#

Comments

1. 

   Frederik Vig 9 months ago

   Same approach as you with the Dictionary collection, but still good read: http://elegantcode.com/2009/01/10/refactoring-a-switch-statement/ and http://elegantcode.com/2009/01/31/refactoring-the-refactored-switch-statement/.
2. 

   Martin S. 9 months ago

   Thank you for sharing!
   
   It's very common to find code like that in any problem, and the solution looks just classy.
   
   Keep 'em coming Joel!
3. 

   Johan Pettersson 9 months ago

   Nice one!
4. 

   Kalle Hoppe 9 months ago

   Yeah, this is a much cleaner and nicer way of doing the same thing. The thing I like most is the part when you only have to do one check, if it exists, execute!
5. 

   Dan Jansson 9 months ago

   Nice post! Currently I'm experimenting a lot with generics and delegates and I just love it and think it's neat! I will try out your example a.s.a.p.
6. 

   Jeff Doolittle 8 months ago

   I find myself doing a lot of this as well, but there is one thing I still don't like about the dictionary implementation you've posted. I still have to remember to register my delegates (actionMap.Add()).
   
   What I've done lately is to create an interface and then set up my concrete class to receive an array of that interface type in its constructor. Then I set up my IoC container (StructureMap) to find all instances which implement the interface and inject them into my concrete class. This way, when I create a new implementation of the interface, it will auto-magically be included in the array parameter passed to my concrete class!
   
   This may be overkill when you have only three search types. But as the number grows, it becomes much easier to manage each of these in their own class file.
   
   If you want to try this out, just cut and past the code below into a new console application .cs file (also make sure your new project has a reference to StructureMap).
   
   So, for example:
   
   

       public class Fruit
       {
           // fruit properties and other implementation would go here
       }
   
       public enum SearchType
       {
           Bananas,
           Oranges,
           Kiwis
       }
   
       public interface IFruitSearch
       {
           bool ShouldApply(SearchType searchType);
           IEnumerable Search();
       }
   
       public class BananaSearch : IFruitSearch
       {
           public bool ShouldApply(SearchType searchType)
           {
               return searchType == SearchType.Bananas;
           }
   
           public IEnumerable Search()
           {
               // search for bananas
               return new Fruit[] { }; // you would actually search for and return fruit here
           }
       }
   
       public class OrangeSearch : IFruitSearch
       {
           public bool ShouldApply(SearchType searchType)
           {
               return searchType == SearchType.Oranges;
           }
   
           public IEnumerable Search()
           {
               // search for oranges
               return new Fruit[] { }; // you would actually search for and return fruit here
           }
       }
   
       public class KiwiSearch : IFruitSearch
       {
           public bool ShouldApply(SearchType searchType)
           {
               return searchType == SearchType.Oranges;
           }
   
           public IEnumerable Search()
           {
               // search for Kiwis
               return new Fruit[] { }; // you would actually search for and return fruit here
           }
       }
   
       public class FruitFinder
       {
           private readonly IFruitSearch[] _filters;
   
           public FruitFinder(IFruitSearch[] filters)
           {
               _filters = filters;
           }
   
           public IEnumerable GetFruit(SearchType searchType)
           {
               foreach (var filter in _filters)
               {
                   if (filter.ShouldApply(searchType)) return filter.Search();
               }
               return new Fruit[] { };  // you would provide a fall through method here if no applicable filter was found
           }
   
           public IEnumerable Filters // only exposed to demonstrate that filters are being properly injected from StructureMap
           {
               get
               {
                   return _filters;
               }
           }
       }
   
       public static class Program
       {
           public static void Bootstrap()
           {
               ObjectFactory.Configure(
                   x => x.Scan(
                   s =>
                   {
                       s.AssemblyContainingType();
                       s.WithDefaultConventions();
                       s.AddAllTypesOf();
                   }
                   ));
           }
   
           public static void Main()
           {
               Bootstrap();
               var finder = ObjectFactory.GetInstance();
               Console.WriteLine(string.Format("Resolved {0} filters for FruitFinder", finder.Filters.Count()));
               Console.ReadKey();
           }
       }
   
   
7. 

   Jeff Doolittle 8 months ago

   Sorry, forgot to replace my angle brackets in that last comment. Let me know if you want me to repost.
8. 

   Natural Makeup 8 months ago

   Nice Code mate and nice guide. I will find these very useful in my school homework's, where we are quite often using C++.
   
   Also I wish a great year 2010 to you.
9. 

   Visual C# Kicks 7 months ago

   Pretty cool approach. Although I'm intrigued by the method Jeff described too.
10. 

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