Installing SQL CE 2.0 and SQL Mobile on a Storage Card

I have just published an article that describes the techniques required to install SQL CE 2.0 and SQL Mobile on a storage card in a Windows Mobile 2003 device. You can read the article here.

Supporting Visual Basic 6

It's very interesting to see that old VB6 is still being used by a very large number of developers. When I started to develop my component products, I always thought that the safest bet would be to provide a very low-level C API and use it to build higher-level components in C# for the .NET world.

This experience has been quite easy because the .NET Framework has lots of classes and mechanisms to suport marshalling and binary data conversions, so the supporting API can really be made very basic indeed. Not so with VB6.

Visual Basic 6 is a very old progamming language and (I think) it lacks the skills required to qualify as a systems development language. My case is quite simple. After shipping the first version of DesktopSqlCe (which only supported C and .NET), I started to get a lot of requests to port the higher level code to Visual Basic 6. And that is the unfortunate work I am doing right now.

My major gripe is the apparent lack of functions to convert from the language types to binary streams (C++: why do you need functions for that ???). The .NET Frameworks has a bewildering number of conversion classes, but VB6 lacks almost everything. Bottom line: I am adding a lot more functions to the low-level API so that VB6 can talk to it...

And yes, I am adding VARIANT support to the code...

K-Jam and ToolHelp

My good friend Cristiano Severini has just published his first Windows Mobile application: CSB (standing for Call and SMS Blocker). One of the chores CSB must accomplish is to shut down tmail.exe during setup in order to install MAPI filters. The setup process finishes with a soft-reset, restoring all processes.

To shut down a process, you must get a handle to it and this is usually done through the ToolHelp API. This API creates a static snapshot of all running processes and allows the application to enumerate them and kill these processes at will. Interestingly, this technique worked quite well until Cristiano tested it in a K-Jam. Being the fortunate owner of one, I was volunteered to help (forced, actually) and found out that the CreateToolhelp32Snapshot funtion would fail every time when called with the TH32CS_SNAPPROCESS flag.

Thanks to one very clever fellow MVP (Paul Tobey) and Microsoft employee (Ilya Tumanov), I now know that this function was failing because it was generating way too much data in the snapshot. To limit the amount of data it generates, one needs to add another flag: TH32CS_SNAPNOHEAPS. Interestingly, this flag is not defined in tlhelp32.h file, where it was supposed to be. Here it is, with my thanks to Paul and Ilya:

// optimization for text shell to not snapshot heaps
#define TH32CS_SNAPNOHEAPS 0x40000000