Migrating from ASP Classic to .NET and pain mitigation

Question

We're in the process of redesigning the customer-facing section of our site in .NET 3.5. It's been going well so far, we're using the same workflow and stored procedures, for the most part, the biggest changes are the UI, the ORM (from dictionaries to LINQ), and obviously the language. Most of the pages to this point have been trivial, but now we're working on the heaviest workflow pages.

The main page of our offer acceptance section is 1500 lines, about 90% of that is ASP, with probably another 1000 lines in function calls to includes. I think the 1500 lines is a bit deceiving too since we're working with gems like this

function GetDealText(sUSCurASCII, sUSCurName, sTemplateOptionID, sSellerCompany, sOfferAmount, sSellerPremPercent, sTotalOfferToSeller, sSellerPremium, sMode, sSellerCurASCII, sSellerCurName, sTotalOfferToSeller_SellerCurr, sOfferAmount_SellerCurr, sSellerPremium_SellerCurr, sConditions, sListID,  sDescription, sSKU, sInv_tag, sFasc_loc, sSerialNoandModel, sQTY, iLoopCount, iBidCount, sHTMLConditions, sBidStatus, sBidID, byRef bAlreadyAccepted, sFasc_Address1, sFasc_City, sFasc_State_id, sFasc_Country_id, sFasc_Company_name, sListingCustID, sAskPrice_SellerCurr, sMinPrice_SellerCurr, sListingCur, sOrigLocation)

The standard practice I've been using so far is to spend maybe an hour or so reading over the app both to familiarize myself with it, but also to strip out commented-out/deprecated code. Then to work in a depth-first fashion. I'll start at the top and copy a segment of code in the aspx.cs file and start rewriting, making obvious refactorings as I go especially to take advantage of our ORM. If I get a function call that we don't have, I'll write out the definition.

After I have everything coded I'll do a few passes at refactoring/testing. I'm just wondering if anyone has any tips on how to make this process a little easier/more efficient.

Answer 1

Believe me, I know exactly where you are coming from.. I am currently migrating a large app from ASP classic to .NET.. And I am still learning ASP.NET! :S (yes, I am terrified!).

The main things I have kept in my mind is this:

• I dont stray too far from the current design (i.e. no massive "lets rip ALL of this out and make it ASP.NET magical!) due to the incredibly high amount of coupling that ASP classic tends to have, this would be very dangerous. Of course, if you are confident, fill your boots :) This can always be refactored later.
• Back everything up with tests, tests and more tests! I am really trying hard to get into TDD, but its very difficult to test existing apps, so every time I remove a chunk of classic and replace with .NET, I ensure I have as much green-light tests backing me as possible.
• Research a lot, there are some MAJOR changes between classic and .NET and sometimes what can be many lines of code and includes in classic can be achieved in a few lines of code, think before coding.. I've learnt this the hard way, several times :D

Its very much like playing Jenga with your code :)

Best of luck with the project, any more questions, then please ask :)

Answer 2

After I have everything coded I'll do a few passes at refactoring/testing. I'm just wondering if anyone has any tips on how to make this process a little easier/more efficient.

Normally I'm not a fan of TDD, but in the case of refactoring it really is the way to go.

Write some tests first which verify what the bit you're looking at is actually doing. Then refactor. This is a LOT more reliable than just 'it looks like it still works.'

The other huge benefit to this is that when you're refactoring something which is further down the page, or in a shared library or something, you can just re-run the tests, as opposed to finding out the hard way that a seemingly unrelated change was actually related

Answer 3

You're going from classic ASP to ASP with 3.5 without just re-writing? Skillz. I've had to deal with some legacy ASP @work and I think it's just easier to parse it and re-write it.

Answer 4

A 1500-line ASP page? With lots of calls out to include files? Don't tell me -- the functions don't have any naming convention that tells you which include file has their implementation... That brings back memories (shudder)...

It sounds to me like you have a pretty solid approach -- I'm not sure if there is any magical way to mitigate your pain. After your conversion effort, the architecture of your app will still be messy and UI-heavy (i.e. code-behind running workflows), and it will probably still be fairly painful to maintain, but the refactoring you are doing should definitely help.

I hope you have weighed the upgrade you are doing against just rewriting from scratch -- as long as you are not intending to extend the app too much and you are not primarily responsible for maintaining the app, upgrading a complex workflow-based app like you are doing may be cheaper and a better choice than rewriting it from scratch. ASP.NET should give you better opportunities to improve performance and scalability, at least, than Classic ASP. From your question I imagine that it is too late in the process for that discussion anyway.

Good luck!