Com Vb6

Introduction: The COM Control Dilemma in VB6

As a developer maintaining legacy VB6 applications, you may be familiar with the challenges of integrating COM controls for improved performance, especially when working with asynchronous programming. One significant issue you might encounter is the inability of the VB6 IDE to unload a COM control once it’s registered, leading to file locks that hinder recompilation efforts in Visual C++ (VC6).

In this blog post, we’ll delve into the problem of unloading COM controls in VB6 and provide a solution that keeps your development environment efficient and frustration-free.

Understanding the Problem

When you register a COM control in the VB6 IDE, it loads the control into memory, and this remains locked until you close the IDE. This creates a few complications:

  • The DLL file is locked: This locks you out of recompiling changes made in VC6.
  • Inability to use IntelliSense: When utilizing CreateObject(), you’re forced to declare your control as an Object, which means missing out on helpful tools like IntelliSense in VB6.

Given these challenges, developers often seek ways to effectively manage their COM controls to avoid unnecessary interruptions during development.

Solution: Integrating VB6 with VC6

While there might not be a straightforward method to force VB6 to unload a control, there is an effective workaround: running VB6 under VC6.

Step-by-Step Guide

Here’s how to set this up:

  1. Load up VC: Start with Visual C++ getting ready for your development work.

  2. Open Your COM Project: Locate and open the project that contains your COM objects within VC.

  3. Edit Your Control: Make any changes or edits necessary for your COM control.

  4. Set the Output Executable: In VC, set the output executable to VB6.EXE and include the appropriate command-line arguments to load your VB6 workspace.

  5. Launch the VB6 IDE: Hit F5 to run the VB6 IDE and load your VB6 project.

  6. Recompile and Repeat: Whenever you need to make adjustments to your COM code, simply exit VB6.EXE, apply your changes in VC, and hit F5 to restart VB6 again. Your workspace will remember settings, keeping your environment organized.

Advantages of this Method

Using this approach offers several key benefits:

  • Debugging with Breakpoints: You can set breakpoints in your COM object, allowing for comprehensive debugging with a full source debugger.

  • Simultaneous Debugging: Work in both C++ and VB without losing track of changes.

  • Always Use the Latest DLLs: Every instance of VB6 running will reference the latest version of your COM DLLs, preventing the stale state that can occur when VB6 holds onto an old version.

Conclusion

By integrating VB6 with VC6 and managing your development workflow through this clever setup, you can circumvent the frustrating limitations of the VB6 IDE with respect to COM control loading. This method not only aids in keeping your DLLs up to date but also enhances your development experience by enabling smoother debugging and iteration.

Explore this approach during your next VB6 project and notice the positive difference it makes in your productivity. Happy coding!