We have a 12-year-old Ms Access app that we use for our core inventory warehousing and invoicing system. It IS already running on an SQL Server backend, but all the ‘logic’, forms and reports are in Access. After experiencing the massive amounts of maintenance sludge it took to turn inventory transactions from non-temporal to temporal, I realized that I need to someday convert this thing into code so I can better manage the logic in a much more maintainable and testable environment.
What are some techniques that would allow me to convert it into a .Net application in a manageable and efficient manner?
One idea was to convert the queries to stored procedures, then convert the app into an Adp project.But I am still clueless as to how to handle the forms and reports.
Also, I am the only developer for my company, if that matters.
As you already have asp.net with some business logic you could open this up to access as a web service (asmx files). Google for the Microsoft Office Web Services Toolkit for your version of access (xp/2003 etc.) and this will write vba proxy classes for you to call the web service. You can bind web service data to the forms through code (vba to read and write to controls) or create local temp tables with data from the web service and use regular access binding.
Depending on what you are most comfortable with (code/tsql) you can put logic in stored procedures or in a business logic layer or hybrid (both). I find it easier to test code than stored procedures and like not being bound to sql server for business logic i.e. if you want to change the database or want to develop/test components offline without a database. New .net features such as LINQ have pretty good performance so you don’t have to rely on stored procedures for database activities.
Keep the access front end user interface until you have refactored all your business logic/data access to web services. You can then create an asp.net app that consumes the web services or a winform app if you want. (Stay clear of wpf, as a ui, for the time being as it is a steep learning curve and doesn’t yet have a datagrid that can compare to the access datasheet view.)
Reports
The access reports can can be upsized to sql server reporting services (vba in reports doesn’t upsize and it is better to write some tsql in stored procedures). If you don’t have the full sql server product you can still use the reportviewer control to write you reports (see http://www.gotreportviewer.com/) in asp.net (or winform with the standard version or up of Visual Studio) binding to ado.net datasets.
Other options: You can write .net dlls and use com interop. This approach allows you to start writing functionality gradually. Don’t use .net ui e.g. a winform as it won’t play nicely with access ui. You could write business logic or data access logic and then call these classes from vba. You can then move this code to asp.net or web services if required.
Things to rule out:
I don’t like the approach of writing a new app with side by side versions. As a single developer you have enough to worry about. You will probably end up adding features in both versions and debugging two versions rather than one.
The vb6 forms interop does not work for access.
ADP as stated is pretty dead. (I never liked them as I often use local tables to optimize performance and they can only be called through code and not linked)
You may be able to convert your vba modules and class modules to vb.net using The Visual Basic Upgrade Wizard (in visual studio) but it doesn’t upsize everything (e.g. dao/ado code to ado.net code) and doesn’t create code that is optimized for .net and may not be easy to write unit tests on depending on the design of the vba code. I recommend rewriting the code (try Test Driven Development if you are serious about testing to see if you like it).