How to implement a single business logic layer based on CSLA and consume it from WPF, Winform and Silverlight?

Question

Is it possible to have a single implementation of business logic layer (based on CSLA) and consume it from different presentation technoligies like winform, silverlight etc. There exists CSLA for silverlight. Does that mean implementing and maintaining different BLL for different presentation technologies.

Any help would be appreciated.

Answer 1

This is very possible with CSLA. The main difference with using your BLL with different UI technologies is the use of the Begin & Callback mechanism of data portal calls in CSLA for Silverlight. If you use this mechanism for all your UI technologies, this would allow you to use the same BLL.

I would suggest that you use separate Factory objects for your BLL so you can decide when to use the BeginInvoke & Callback mechanism and your business objects would be untouched.

You could also create duplicate factory methods if you felt that was necessary. For example if you had a business object of Customer:

public class Customer : Csla.BusinessBase<Customer>
{
    private Customer() { }

    private void DataPortal_Fetch(SingleCriteria<Customer, int> criteria)
    { // populate here }

}

Then you could have a CustomerFactory object that contained both methods for Silverlight and the other UI technologies:

public static class CustomerFactory
{
    // Handle most UI needs
    public static Customer Fetch(int id)
    {
        return DataPortal.Fetch<Customer>(new SingleCriteria<Customer, int>(id));
    }

    // Handle Silverlight needs
    public static void Fetch(int id)
    {
        DataPortal.BeginFetch<Customer>(id, FetchCallback); 
    }

    private static FetchCallback(object sender, DataPortalResult<Customer> result)
    {
        // notify the UI of result.Object
    }
}

You could also get a little more clever and implement dependency injection via an IoC container to make the call to your factory methods a little more smart.

The bottom line is that your actual business objects will not change but your factory objects may have duplicate CRUD methods in certain circumstances.

Rocky actually has a sample (ProjectTracker) that implements a single BLL with multiple UI layers at his web site (listed under 'Samples' at http://www.lhotka.net/cslanet/Download.aspx)

Answer 2

Hello,

This is very easy todo with the CodeSmith CSLA templates. We have a PetShop Silverlight MVVM and Web sample application located here that shows off the generated code.

Thanks -Blake Niemyjski (Author of the CodeSmith CSLA Templates)