vb6-interop_skill

Overview

This skill documents classic VB6 patterns, COM interop techniques, and practical strategies to migrate VB6 code to modern VB.NET. It focuses on reducing risk with incremental migration, correct COM object management, and replacing legacy idioms with safe .NET equivalents. The goal is maintainable, interop-safe applications during and after migration.

How this skill works

The skill inspects common VB6 constructs (Variants, default properties, On Error) and maps them to explicit VB.NET patterns (strong typing, properties, Try-Catch). It outlines both early and late COM binding approaches, demonstrates proper COM release patterns, and shows how to create and register COM-visible .NET components. It also presents an incremental migration workflow using wrappers and gradual replacement.

When to use it

• You need to modernize a VB6 application while keeping it runnable during migration.
• When integrating VB.NET code with existing COM components or Office automation.
• To eliminate memory leaks by applying correct COM object cleanup patterns.
• When designing new .NET components that must be consumed by legacy COM clients.
• When converting VB6 error handling, file I/O, or collection usage to safe, typed .NET equivalents.

Best practices

• Enable Option Strict and Option Explicit for safety and clearer conversions.
• Prefer early binding with generated interop assemblies when possible for clarity and performance.
• Always release COM objects in reverse creation order, call Quit/Close, set to Nothing, and force GC when required.
• Use Try-Catch and typed exceptions instead of VB6 On Error patterns.
• Adopt generic collections, Using blocks, and async I/O in new code; avoid Microsoft.VisualBasic.Compatibility.VB6.

Example use cases

• Wrap a VB6 COM component with a thin VB.NET wrapper to incrementally replace legacy logic.
• Export DataTable to Excel using early-bound interop and ensure all COM objects are released to avoid orphaned Excel processes.
• Create a COM-visible .NET Calculator class with GUIDs and interface attributes for legacy consumers.
• Replace VB6 file handling with Using/StreamWriter and migrate to asynchronous file APIs where latency matters.
• Convert VB6 control arrays to List(Of T) or Dictionary(Of TKey,TValue) and refactor UI code accordingly.