Putting a new web interface on an old fat-client database_问答_开发者

My company has a fairly old fat client application written in Delphi. We are very interested in replacing it with a shiny new web application. This will make maintenance a breeze and many clients want a web application.

The application is extremely rich in domain knowledge, some of which is out of our control. Our clients use the program to manage their own clients and report them to the government. So an inaccurate program is a pretty big thing. The old program has no tests. We are not sure yet if we will implement automated testing with the new one.

We first planned to basically start from scratch. But we are short handed and wanting to basically get everyone on the web as soon as possible. So instead of starting from scratch we've decided to try to make use of the legacy fat-client datab开发者_运维知识库ase.

The database is SQL Server and can be used in SQL Server 2008 easily. It is very rich in stored procedures, functions, a few triggers, and lots of tables with over 80 columns... But it is decently normalized. We want for both the web application and fat client to be capable of using the same database. This is so that if something breaks badly in the web application, our clients can still use the fat client and connect to our servers. After the web application is considered "stable", we'd deprecate the fat client.

Has anyone else done this? What tips can you give? We want to, after getting everyone on the website, to slowly change the database structure to take care of some design deficiencies. What is the best way to keep this in a data access layer so that later changes are easy?

And what about actually making the screens? Is there any way easier than just rewriting an 80 field form in ASP.Net? Are there any tools that can make this easier?

The current plan is to use ASP.Net WebForms (.Net 3.5). I'd really like to use MVC, but no one on the team knows it including me.

We are not sure yet if we will implement automated testing with the new one.

Implement automated testing. What's the point in replacing one buggy program with another?

Good question, but "Slowly change" the db structure after getting everyone on the website, sounds like a joke...
I would rather take the opportunity to create a fresh db structure, write a bulletproof migration script for you db, that you can try out and rewrite a zillion times without any side effect fro your clients, and then write whaterver you want (fat/web) on the new db, have it tested and migrate everyone when it's ready.

I have a couple suggestions:

1) create a service layer to abstract away the dependance on the DAL. In a situation as you describe having a layer of indirection for the UI and BLL to rely on makes DB changes much safer.

2) Create automated tests (both unit and integration), especially if you plan on making fairly significant changes to the Domain or Persistance layers (BLL/DAL). To make this really easy you should always try to program to an interface. This makes your code more flexible as well as letting you use mocking frameworks (Moq is one I like) to ensure your tests truely are unit tests and not integration tests.

3) Take a look at DDD (http://domaindrivendesign.org/) as it seems to fit pretty well with the given scenario. At the very least there are some very useful patterns that can help make your application more flexible.

4) MVC isnt very hard to learn at all, it is however an easy way to get unit testing setup for the UI as a result of the MVC architecture (testing the controller and not the view). That said, there is no reason you couldn't unit test web forms, its just a bit more work. MVC really is just a UI framework/design pattern (more Model2 but we can ignore that for now). It gets you closer to the metal so to speak as you will be writting a lot more HTML and using a Model (the 'M') for passing data around.

For DDD take a look at Eric Evans book: http://www.amazon.com/Domain-Driven-Design-Tackling-Complexity-Software/dp/0321125215/ref=sr_1_1?s=books&ie=UTF8&qid=1317333430&sr=1-1

Hope that helps

ASP.NEt forms is a no starter, is completely inappropriate for something like this. I recommend to start with something like Creating an OData API for StackOverflow including XML and JSON in 30 minutes, then build your Web app on top of that (ie. push it to the client, use JQuery/Silverlight).