.NET Interoperability Features and Legacy Code

Existing code that uses ActiveX, COM, or COM+ can be integrated into .NET application development. You can also call to the Windows API (Application Programming Interface) from .NET. The ability to use legacy code from .NET applications may save you considerable time over writing everything from the ground up. The interoperability features of .NET can handle legacy code in many ways:

• ActiveX ActiveX controls can be placed on Windows forms.

• COM/COM+ These components can be instantiated and invoked by .NET code.

• Windows API The Windows API may be invoked using the Platform Invoke capability ( PInvoke ) within .NET applications.

The interoperability of .NET code is two-way. Although this chapter focuses on calling COM components from .NET code, you can also call .NET components from COM code.