Calvin Hsia's WebLog

Remote Desktop (mstsc.exe) is great: it allows me to access another remote machine as if I were sitting at its keyboard and seeing its screen. My web server sits on top of a 7 foot tall bookcase but I have no need to touch it: I can use RD from other...

In my blog about Dr. Watson I talked about product crashes. What is an example of a crash? How destructive is it? Here’s a simple example. MyFunction takes a string parameter and calculates its length MyFunction ( char * StringParam...

Sometimes it’s useful to make your application run as a service. A service can run without any user logged in, can automatically start upon reboot, and can survive user logoffs. It can also run as a different user with different access rights. Normally...

Here is some code to demonstrate the AutoComplete property Its behavior is very similar to Outlook 2003 or the Internet Explorer Address URL entry control. It prompts the user with possible entries in a drop down like Intellisense. The code creates...

Try this on Windows XP or Vista (I don’t remember if manifests are allowed on Win2000: can someone confirm please? Thanks) Start Notepad, then choose File->Open and navigate to c:\windows\system32\notepad.exe and click Open. Hit Ctrl-F to...

Here’s some interesting code to run. It starts Microsoft Word and binds some Fox code to some Word events. Type some text into the document. Select some text. When the Selection Change event occurs, the Foxpro code creates the speech API object...

I wanted to add the ability to zoom into a portion of a photograph on my photo viewer. Below is some code that processes the MouseUp, MouseDown and MouseMove events to add a yellow dotted-dash selection rectangle using a Shape control that the mouse can...

Creating an ActiveX control is a good exercise in understanding how one works. It also helps to have full control over its source code for learning and testing purposes. A customer asked about migrating legacy ActiveX controls over to .Net. Many controls...

When FoxPro opens or uses a table or cursor, internally we have to keep track of the field names used in that table. For example, this statement creates a table with 3 fields. CREATE TABLE foo ( lastname c( 10 ), firstname c( 10 ),address c( 20 )) When...

My 7 year old daughter Wendy has been clamoring for her own email account, among other things (like her own cell phone). She’s been using a computer for years, and has been using my old web server laptop as her main machine, mainly to surf kids...

On most Blogs, there is a link called “Syndication”,”RSS”, or “XML” that is the RSS feed. Click on that, and you see an XML document that contains some recent blog posts. This simple code reads the RSS feed for my blog, does an XSLT transform of the XML...

We have heard a couple reports of strange behavior in Visual FoxPro if you click on a thumb button in a scrollbar, drag it up or down a little, then pause for 6 seconds or so. The contents of the window would disappear, leaving a blank editing window...

When you run your VB or C# application, you might get an OutOfMemoryException thrown, even if your machine has lots of memory. Every 32 bit process has a 2^32 bit (4 Gig) address space. That means every pointer has a size of 32 bits (4 bytes) and...

I wanted to update a couple zip files of the VB version of my Blog Crawler (to be posted soon) with the latest and greatest when I built the Release version of a project. I used the XCOPY command with the /D option to update only if changed. Copying to...

In the old days, computers had blinking lights. Indeed, old movies used to show computers working with blinking lights and tape reels moving back and forth. My school computer was a PDP-8/L with a whopping memory of 4K 12 bit words back in 1971. (Here...

At the SouthWest Fox conference in Phoenix I asked “How many people have Visual Studio?” Almost everybody raised their hand. Then I asked “How many people have used it?” Very few hands were raised. Here’s a simple way to create some VB.Net code and call...

As a long time software company, Microsoft has certain procedures to follow when releasing software to the public. A change to the policy was instituted at Microsoft last year. A brand new tool would scan all released software to see if any “undocumented...

What does it mean to make code more maintainable? Certainly obfuscated code is hard to understand, by definition. A big part of maintainability is making it easier for others to read and understand what the code is doing. Your code may have been...

Here’s some C++ code to host the CLR. It’s an alternative to using COM Interop (s ee A Visual Basic COM object is simple to create, call and debug from Excel ), or using a User Control (see Create a .Net UserControl that calls a web service that acts...

It’s often very useful to be able to execute a SQL SELECT statement on a text file. I was debugging a multiprocess multithread Foxpro COM DLL problem in a COM+ application . To help diagnose the problem, I wanted to figure out the sequence...

Now that Las Vegas Devcon is over, I’ll be posting some of my sample code from the keynote and my session here. I demonstrated how to make a simple VFP screen saver. To test it, invoking it immediately is useful. Windows XP allows you to have a screen...

VFP allows you to generate COM servers using the OLEPUBLIC keyword. These objects can have custom properties. For example, a Customer object can have an Address property of type string. Other client applications (VFP, Excel, VB.Net, VB Script) can...

Today’s digital cameras take pictures with much higher resolution than many computer screens. My Canon PowerShot SD800 IS camera takes pictures at 3072 x 2204 resolution. One of my laptops died recently, and I noticed that local laptop retailers...

Here’s how you can use Visual Studio to create a .Net User Control that will act as an ActiveX control that can be used in Excel (or other Office application), VB6 or Foxpro. This will bring the power of the entire.Net Framework to your program. This...

Warning: this simple program produces mesmerizing spirographic images that seem hallucinatory in nature! Discretion is advised! Do not drive while watching these graphics! Almost 30 years ago, I had heard about a concept developed by Professor...