Question

I have inherited an application that is logically split into 4 tiers, but physically resides across two. The 4 logical tiers are:

1. asp.net website
2. business logic in a C# .Net assembly (referenced from website)
3. data access c# assembly – classes generated by codesmith tool (referenced from business logic)
4. sql server database

An example of the way that the website interacts with the business layer is:

Booking b = new Booking();
b.property1 = x;
b.property2 = y;

result = b.method();

ie. it sets the data on public properties of the biz class then executes a method that in-turn reads from the properties.

Unfortunately, there are lots of properties and some of these are not base types, they are other objects eg the Booking object contains collection of Vouchers objects

I need to make the tiers 2-4 available to a new user interface (a very different website that will serve in-store kiosks).

I would like to expose the business layer through WCF. I have created an IBooking interface, defined the method signatures and decorted with [OperationContract] etc. Where I’m stuck is how to manage the data. I realise that I could define a data contract to match the various public properties of the Booking object but then I would need to make significant changes to the existing website – rather than it setting the properties and calling a method withouth parameters it would need to populate an instance of the data contract and pass this as a parameter to every method call.

Could anyone advise on the best way to approach this please. I am able to make changes to the exisiting website but I’d like to keep these to a minimum.

Many thanks,

Rob.

Answer 1

I’d suggest the simplest means of implementing this would be to create a WCF wrapper around your existing business logic without altering your current website. This can be done without any (significant) code changes to what you already have. The ‘downside’, if you consider it such, is that your existing website won’t use your WCF services.

You’ve already created an contract for the service. If you haven’t already, create message contracts for the operation parameters. Then you can create your ‘new’ website by working with the service contract & message contracts.

Services are different to OO, in that you don’t normally set properties & then call parameterless methods – instead you invoke an operation and include any relevant, required data at the same time. Your service implementation – the class that implements the IBooking contract – will do the work of

• instantiating your existing classes
• populating those objects
• calling the parameterless methods, and
• returning results.

e.g.

// contract
[OperationContract]
MyResponseMessage DoMethod(MyResultRequest requestData);

// and the implementing class (the 'service')
public MyResponseMessage DoMethod(MyResultRequest requestData)
{
    MyResponseMessage responseData = new MyResponseMessage();

    Booking b = new Booking(); 
    b.property1 = requestData.X; 
    b.property2 = requestData.y;
    responseData = b.method(); 
}