Add the following code to the Click method of the Validate button. This code validates the orders table and updates the progress bar.

* Have the label tell what is happening.
ThisForm.label1.Caption = "Validating orders table..."
ThisForm.Refresh
Select orders
* The Min and Max properties set the progress bar's range.
* The Min defaults to 0. Set the Max to the number of 
* records in the orders table.
ThisForm.ocxProgressBar.Max = RECCOUNT()
* Initialize a counter to represent the current record.
i = 1
* Loop through each record in the orders table.
SCAN
    * Set the net amount of the order.
    IF order_net <> (order_amt * order_dsc/100) + freight
        Replace order_net With ;
          (order_amt * order_dsc/100) + freight
    ENDIF
    * The Value is the current position in the range.
    * Set it to the current counter value. The control control knows 
    * when to draw another rectangle based on its size.
    ThisForm.ocxProgressBar.Value = i
    * Increase the counter by 1.
    i = i + 1
ENDSCAN

* Reset the progress bar.
ThisForm.ocxProgressBar.Value = 0
* Have the label report that the operation is finished.
ThisForm.Label1.Caption = "Orders table validated"
ThisForm.Refresh

Save and run the form. Choose Validate to start the validation process. The caption of the label displays what is happening and the progress bar updates steadily until the process is over.

Behind the Scenes

The progress bar has a range and a current position. The range represents the entire duration of the operation. The current position represents the progress the application has made toward completing the operation. ActiveX controls are programmed via their properties and methods, just like Visual FoxPro objects. The Max and Min properties of the ProgressBar control set the limits of the range. The Value property specifies the current postion within the range.

The Min property of the control defaults to zero. The Max property is set to the number of records in the orders table. Therefore, the Max property is the number of records that need to be processed. In addition, a counter variable is created. This will keep track of what record is current.

ThisForm.ocxProgressBar.Max = RECCOUNT()
i = 1

As the code loops through each record, the net amount of the order is checked and recalculated if necessary. The Value property of the progress bar is set to the counter variable. In this example, that means the Value is increased by 1 after each record is validated.

ThisForm.ocxProgressBar.Value = i
i = i + 1

When the Value of the progress bar is changed, the control may or may not draw another rectangle. Remember that the Value property specifies the current position within the range. Because rectangles are used to fill in the control, the amount filled in only approximates the Value property's current value.

Based on the control's size, the Value property determines when to display the next rectangle. The Height and Width properties of the control determine the number and size of the rectangles that fill the control. The more rectangles, the more accurately the control portrays an operation's progress. To increase the number of rectangles displayed, decrease the control's height or increase its width.

Summary

ActiveX controls are a powerful way of reusing components to speed application development and simplify maintenance. ActiveX controls enable Visual FoxPro developers to quickly add unique functionality to their applications, and to share that functionality among several development and runtime environments. Visual FoxPro 5.0 has enhanced support for ActiveX controls, making available a wider range of controls for the Visual FoxPro developer. The programming model for ActiveX controls is simple and straightforward, and similar in many respects to Visual FoxPro native objects.

Frequently-Asked Questions

How can I learn more about using ActiveX controls with Visual FoxPro 5.0?

A good place to start is the white paper entitled, "ActiveX Controls and Visual FoxPro 5.0," found on the Visual FoxPro Web site. Also, see Chapter 16, "Adding OLE," in the Developer's Guide, part of the documentation that came with your copy of Visual FoxPro 5.0.

Can Visual FoxPro 5.0 create ActiveX controls?

Visual FoxPro is an application development environment that focuses on assembling applications from components, rather than on building components per se. Microsoft provides several tools for component creation (Visual C++®, Visual Basic®, Visual Basic - Control Creation Edition, Visual J++™).

What other products can use ActiveX controls?

All of the tools in Visual Studio 97™, plus Microsoft® Office 97 and Microsoft® Internet Explorer. ActiveX controls are a standard component of Windows, so many other third-party products support them as well.

How are a control's properties and methods documented?

In many cases, controls install with help files (.HLP) which describe how to program them. In cases where no help files are included, developers can use an Object Browser which ships with several other Microsoft tools, to inspect the control's properties, events, and methods.

Can I obtain an evaluation copy of Visual FoxPro 5.0?

Visual FoxPro 5.0, and all Microsoft products, are available with a 30-day money back guarantee from software resellers. Therefore, if you purchase the product on a trial basis, and decide not to keep it, simply return it for a full refund.

How do I get the Visual Basic Control Creation Edition (VBCCE)?

Visual Basic - Control Creation Edition is free, available for download. Please see www.microsoft.com/vbasic/ for more information.