Porting a PowerBuilder Application to .NET

Question

Does anyone have any advice for migrating a PowerBuilder 10 business application to .NET?

My company is considering migrating a legacy PB application to .NET (C#) and I am just wondering if anyone has any experience - good or bad - that you would like to share.

The application is rather large with 10 PBL libraries, some PFC as well as custom frameworks. There are a large number of DLL calls being made as well. Finally, it uses a Microsoft SQL Server database.

We have discussed porting the "core" application code to .NET and then porting more advanced functionality across as-needed.

Answer 1

When I saw the title, I was just going to lurk, being a renowned PB bigot. Oh well. Thanks for the vote of confidence, Bernard.

My first suggestion would be to ditch the language of self-deception. If I eat half of a "lite" cheesecake, I'm still going to lose sight of my belt. A migration can take as little as 10 minutes. What you'll be doing is a rewrite. The time needs to be measured as a rewrite. The risk needs to be measured as a rewrite. And the design effort should be measured as a rewrite.

Yes, I said design effort. "Migrate" conjures up images of pumping code through some black box with a translation mirroring the original coming out the other side. Do you want to replicate the same design mistakes that were made back in 1994 that you've been living with for years? Even with excellent quality code, I'd guess that excellent design choices in PowerBuilder may be awful design choices in C#. Does a straight conversion neglect the power and strengths of the platform? Will you be living with the consequences of neglecting a good C# design for the next 15 years?

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That rant aside, since you don't mention your motivation for moving "to .NET," it's hard to suggest what options you might have to mitigate the risk of a rewrite. If your management has simply decided that PowerBuilder developers smell bad and need to be expunged from the office, then good luck on the rewrite.

If you simply want to deploy Windows Forms, Web Forms, Assemblies or .NET web services, or to leverage the .NET libraries, then as Paul mentioned, moving to 11.0 or 11.5 could get you there, with an effort closer to a migration. (I'd suggest again reviewing and making sure you've got a good design for the new platform, particularly with Web Forms, but that effort should be significantly smaller than a rewrite.) If you want to deploy a WPF application, I know a year is quite a while to wait, but looking into PowerBuilder 12 might be worth the effort. Pulled off correctly, the WPF capability may put PowerBuilder into a unique and powerful position.

If a rewrite is guaranteed to be in your future (showers seem cheaper), you might want to phase the conversion. DataWindow.NET makes it possible to to take your DataWindows with you. (My pet theory of the week is that PowerBuilder developers take the DataWindow for granted until they have to reproduce all the functionality that comes built in.) Being able to drop in pre-existing, pre-tested, multi-row, scrollable, minimal resource consuming, printable, data-bound dynamic UI, generating minimal SQL with built-in logical record locking and database error conversion to events, into a new application is a big leg up.

You can also phase the transition by converting your PowerBuilder code to something that is consumable by a .NET application. As mentioned, you can produce COM objects with the PB 10 you've got, but will have to move to 11.0 or 11.5 to produce assemblies. The value of this may depend on how well partitioned your application is. If your business logic snakes through GUI events and functions instead of being partitioned out to non-visual objects (aka custom classes), the value of this may be questionable. Still, this is a design faux pas that should probably be fixed before a full conversion to C#; this is something that can be done while still maintaining the PowerBuilder application as a preliminary step to a phased and then a full conversion.

No doubt I'd rather see you stay with PowerBuilder. Failing that, I'd like to see you succeed. Just remember, once you take that first bite, you'll have to finish it.

Good luck finding that belt,

Terry.

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I see you've mentioned moving "core components" to .NET to start. As you might guess by now, I think a staged approach is a wise decision. Now the definition of "core" may be debatable, but how about a contrary point of view. Food for thought? (Obviously, this was the wrong week to start a diet.) Based on where PB is right now, it would be hard to divide your application between PB and C# along application functionality (e.g. Accounts Receivable in PB, Accounts Payable in C#). A division that may work is GUI vs business logic. As mentioned before, pumping business logic out of PB into executables C# can consume is already possible. How about building the GUI in C#, with the DataWindows copied from PB and the business logic pumped out as COM objects or assemblies? Going the other way, to consume .NET assemblies in PB, you'll either have to move up to 11.x and migrate to Windows Forms, or put them in a COM callable wrapper.

Or, just train your C# developers in PowerBuilder. This just may be a rumour, but I hear the new PowerBuilder marketing tag line will be "So simple, even a C# developer can use it." ;-)