Refactoring Code to avoid Type Casting

Question

I have following C# code in .Net 4.0. It requires a type casting of IBusiness to IRetailBusiness.

//Type checking
if (bus is IRetailBusiness)
{
       //Typ         


        

Answer 1

Basically, if I understood you right, you want to avoid the type casting.

You can accomplish that simply by changing the constructor signature from:

public RetailInvestmentReturn(IRetailBusiness retail) {...}
public IntellectualRightsInvestmentReturn(IIntellectualRights intellectual) {...}

to:

public RetailInvestmentReturn(IBusiness retail) {...}
public IntellectualRightsInvestmentReturn(IBusiness intellectual) {...}

If that is not an option due to design constraints, then you can try to use the strategy pattern. That would still need a type cast, but you would get rid of the terrifying "ifs" and "elses", that, I believe, is your real question, right? In order to do that you need to:

1. Create a dictionary with the "type" and the "method to run"
2. Use it!

In code, that would look something like this:

1. (Create,...)

       Dictionary> dict = new Dictionary>
       {
           {typeof (BookShop), business => new RetailInvestmentReturn((IRetailBusiness) business)},
           {typeof (AudioCDShop), business => new IntellectualRightsInvestmentReturn((IIntellectualRights) business)}
       };
   

2. (Use it!)

// try this:

foreach (IBusiness bus in allMyProfitableBusiness)
{
    investmentReturns.Add(dict[bus.GetType()](bus));
}