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

Make the concrete implementations of IBusiness visitable by visitor pattern. then create a visitor in the investment return domain that can visit each business, like this:

public interface IVisitor
{
    T Visit(IIntellectualRights bus);
    T Visit(IRetailBusiness bus);
}

public interface IBusiness
{
    T Accept(IVisitor visitor);
}

public class AudioCDShop : EntityBaseClass, IRetailBusiness
{
     public void Accept(IVisitor visitor)
     {
          return visitor.Visit(this);
     }

//do the same for each IBusiness implementor.

Then in your investment return domain:

 public class InvestmentVisitor : IVisitor
 {
     public InvestmentReturn GetInvestment(IBusiness bus)
     {
          return bus.Accept(this);
     }

     public InvestmentReturn Visit(IIntellectualRights bus)
     {
          return new IntellectualRightsInvestmentReturn(bus)
     }

     public InvestmentReturn  Visit(IRetailBusiness bus)
     {
          return new RetailInvestmentReturn(bus);
     }
 }

Usage

 var investmentReturn = new InvestmentVisitor().GetInvestment(bus);

totally untested and unverified.. but the concept works. This might also be way overkill if you only have two different kinds of nodes that should be visited.