I have made certain choices in my architecture which I request the community to review and comment. I am breaking up the post in smaller sections to make it easier to understand the context and then suggest/comment. I am sorry that the post is long, but is required to explain the context.

What am I building

A typical business application where there are application users, security roles, business operation/action rights based on roles and several business modules like Stock Receive, Stock Transfer, Sale Order, Sale Invoice, Sale Return, Stock Audit etc. and several reports. The application is a WinForm application since it has a lot of rich and responsive UI requirements and has to operate in disconnected mode (with a local SQL Server), most of the time.

What have I done

I have built a framework - nothing to boast about, but just a set of libraries that serves the repetative requirements of my application, e.g. authentication, role based authorization, data access, validation, exception handling, logging, change status tracking, presentation model compliance and reasonable loose coupling between components. No, I have not written everything from scratch, you can say I have consolidated many things together like some concepts from CSLA, Martin Fowler for Presentation Model, blocks from Enterprise Library, Unity etc. to build a set of libraries that will help my developers be productive quickly without having to look up Google for many of the technical requirements. I have tried to keep the framework generic so that it can be used in typical business applications and also tried to follow some best practices that will support the same Business Objects to be used in an ASP.NET MVC environment also.

My present architecture serves my objectives well, and have built several modules (on WinForm) without much trouble. The architecture also lent itself well to build some usable prototype on ASP.NET MVC with the same set of business objects, without changing a single line of code.

My Dilemma

I have used Custom Business Objects since that gives me a clearer OOP representation of the problem scope in my solution scope, and helps me visualize my entire solution as collection of objects with data and behavior rather than having a set of relational data (DataSet) and implement behaviours (business logic, validation) etc. separately. With rich databinding support in .NET 2.0 binding Custom Business Objects to UI was a breeze.

Now while building my business objects, I am still in a dilemma about representation of collections in business objects. Currently I am using DataSets to represent collections while I have seen many suggestions to implement custom collections. For example, in my vision, a typical Sale Invoice Object will contain 'Sales Invoice Items' as a collection. Now theoritically, I can accept that the each 'Sales Invoice Item' should have its own behavior along with their data (ItemCode, Name, Qty, Price etc.) but typically managing of Sale Invoice Items in a Sale Invoice is handled by the Sale Invoice Object itself, e.g. adding/removing Items from collection. Additionally, we can also put business logic/rules for the Sales Invoice Items like "Qty should not be greater than the ordered qty", "Price should be max 10% above the price in Sale Order" etc. in the Sale Invoice object itself.

With that kind of a vision, I felt that most business object child collections can be managed by the parent itself, including add/remove from collection as well and implementing business logic for the collection items, hence the collection items hold nothing but data.

Additionally, typical collections are represented in UI in Grids, where ability to support DataBinding becomes very important for any collection. Implementing a custom collection, in that case would also mean, I have to implement robust DataBinding support as well, for the collection, which is of course time consuming.

Now, considering child collection behaviors are implemented in the parent and the need for DataBinding of child collections, I chose DataSet to represent any child collection in my business objects. In the above example of Sale Invoice I will have 'Invoice Number', 'Date', 'Customer' etc. as attributes of the 'Sale Invoice' but 'InvoiceItems' as a DataSet. Of course, when I say DataSet, it is not a vanilla dataset but an extended DataSet that supports business rule validation and the same role based security model of my framework to allow/deny any business operation to rows/columns of the DataSet, automatically.

This approach has allowed easier collection management and databinding in my business objects and my developers are able to deliver modules rapidly.

Questions

1. Do you feel that the approach is reasonable?

2. Do you see any shortcomings of this approach?

3. I am recently thinking of using 'Typed DataSets' as child collections, for easier representation in code, that will allow me to write 'currentInvoice.InvoiceItems' (for the DataTable) and 'invoiceItem.ProductCode' or 'invoiceItem.Qty', instead of 'drow["ProductCode"].ToString()' or '(int)drow["Qty"]' etc. Does this choice have any demerits?

Thank you if you have read so far and a salute if you still have the Energy to answer.