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The .NET Framework is Microsoft's new programming model for building Web applications, smart client applications, and XML Web services—applications that expose their functionality programmatically over a network using standard protocols such as SOAP, XML, and HTTP. The specification of the .NET Framework is now an international standard, thanks to Microsoft's successful submission of the common language infrastructure (CLI) to the ECMA standards organization, which adopted it in December of 2001. (One of the authors, Emmanuel Stapf from ISE, is a member of the corresponding ECMA Technical Committee.) Although a detailed presentation of the .NET Framework is beyond the scope of this article, we may note the following highlights, of special interest to application developers:

• The architecture relies on a virtual machine, so that compilers for any language always generate the same code, MSIL (Microsoft Intermediate Language).

• The code that gets executed on any actual computer is native (binary) code for that computer, translated incrementally or not, through a process known as just-in-time (JIT) compilation

• The virtual machine's equivalent of an operating system is the common language runtime (CLR), providing a number of crucial facilities—memory management, garbage collection, security, exception handling—to programs regardless of their language or origin (hence the word "common").

• The memory model used by the virtual machine and the CLR does not rely on addresses, bytes, and words; instead, it is an object-oriented model based on the notions of type, class, object, inheritance, polymorphism, typing, and dynamically bound calls.

• The language interoperability mechanisms of the .NET Framework, including the common language runtime, MSIL, the object model, and the Common Language Specification (CLS), enable the various parts of an application to use different programming languages—each chosen to be the best for the job at hand—and to achieve a degree of inter-language cooperation unprecedented in the software world. Not only may a module call a routine written in another module, a class in an object-oriented language may inherit from a class in another, exceptions cross language boundaries, as do debugging sessions—and all this is achieved without any special effort on the programmer's part and without any need for languages to know about each other.

• A new development environment, Visual Studio .NET, provides advanced development facilities—compilation, browsing, debugging, user interface development—and is, like the rest of the technology, open to many languages.

• .NET provides thousands of reusable components extending across many application areas, from localization to networking and language analysis.

• Among the most important component libraries are Microsoft® ASP.NET, an innovative framework for building Web applications and XML Web services; Microsoft® ADO.NET, an object-relational interface library; and Microsoft Windows® Forms for building Windows-based smart client applications.

• These mechanisms are potentially available to developers using any programming language, provided the implementers of that language offer a compiler that's compatible with .NET Framework—not only by generating IL but also by observing the .NET Framework rules of language interoperability.
  

The .NET Framework is attractive to Eiffel users since it follows many of the same ideas that they have accepted as essential to quality software development: use of an object model, automatic garbage collection, and exception handling. It also offers an integrated platform with direct access to thousands of reusable components, the prospect of full interoperability with software elements written in both Eiffel and other languages, and the power of XML Web services and other Internet applications.

For .NET Framework users, Eiffel provides the added value of an advanced object-oriented method and language that covers the entire lifecycle—not just programming, but the whole process starting with analysis and design and continuing with implementation, reuse, extension, and maintenance. Eiffel also offers unique reliability mechanisms such as Design by Contract™, advanced language features such as genericity and multiple inheritance, and the extensive body of reusable components developed by ISE and other parties, including the EiffelBase library of data structures and algorithms and the EiffelVision library for multi-platform graphics.

Eiffel on the .NET Framework provides an ideal combination for companies wishing to take advantage of best-of-breed technologies in operating systems, Internet and Web infrastructure, software development methods, and development environments. In particular, the openness of Eiffel to other languages and environments combined with the .NET Framework's emphasis on language neutrality makes the resulting product an ideal vehicle for building applications containing components in many different languages, Eiffel serving as the glue between them. In the rest of this article, we describe this combination and the challenges we faced when integrating ISE Eiffel into .NET.