At first glance, it may sound like an impossible prospect for .NET developers to engage in cross-platform, open source development in the enterprise. Such a reality would be unfortunate, because many development teams enjoy the productivity inherent in using Visual Studio .NET and its wealth of tools for rapidly producing high-quality code. However, they would also like the ability to deploy on platforms other than Windows.

That is the purpose of the Mono project (www.go-mono.org), an open source implementation of the .NET Framework based on the ECMA International standards for C# and the Common Language Infrastructure.

The Mono project makes the same advanced development technologies embodied in Visual Studio and the .NET Framework available to Windows developers who want to deploy their applications on Linux. Mono also enables Windows developers to bring their applications to Solaris, MacOS X, and other operating systems.

Mainsoft delivers a complementary cross-platform solution that extends Web and server .NET applications to Java. Visual MainWin for J2EE uses many of the Mono libraries and includes an add-in to Visual Studio that cross-compiles Microsoft IL to Java bytecode. Grasshopper, Mainsoft's freely available developer edition, comes bundled with Tomcat and is designed for single CPU deployments. The Enterprise edition supports multiple CPU deployments on enterprise class J2EE servers such as IBM WebSphere Application Server or BEA WebLogic Server. The Portal edition enables enterprises to incorporate their ASP.NET applications and Web Parts into their enterprise WebSphere Portal Server.

The Details of Mono and Multiplatform Deployment
Today, Mono implements many of the components that .NET developers require, including AS4P.NET for Web application development, ADO.NET for database access, and Windows.Forms for rich client applications. The Mono project also provides a C# 2.0 compiler that supports the latest language specifications, including generics, anonymous methods, and iterators, as well as assemblers, linkers and API documentation for these.

Mono supports a wide variety of hardware platforms and operating systems. Its 32-bit ports include the x86 architecture, Sun's SPARC, the embedded ARM processor, and the s390 mainframes. On 64-bits, Mono supports the Itanium, the s390x, and the x86-64 architecture with ports for other platforms following closely.

Mono undergoes a rigorous testing regime necessary to create enterprise-ready software. It makes use of the NUnit test harness, as well as some internal testing frameworks, to run more than 100,000 individual tests designed to ensure functional equivalence with the .NET Framework. If a discrepancy is found, more unit tests are written around that discrepancy so that it is tested thoroughly before being released.

Version 1.2 of Mono, released at the beginning of November, is compliant with and provides full support for .NET 1.1, and partial support for .NET 2.0. In addition to Window.Forms support, Mono version 1.2 includes numerous feature upgrades including full support for C# 2.0, generics, Gtk# 2.0, and significant updates to the .NET 2.0 API.

Mono and Mainsoft provide alternate ways to extend the reach of existing .NET applications across the enterprise by enabling deployment on alternative hardware and operating systems, either on top of the .NET CLR or through cross-compilation to Java bytecode.

When and Where to Use Cross-Platform Development
Mono enables development in C# or Visual Basic .NET on Windows, but deploys on Linux or other platforms supported by Mono. In many cases, it is possible to take a .NET application developed using the Visual Studio .NET IDE and run the resulting binary directly on Mono. For those wishing to keep the business logic in .NET but use a native Linux UI, Gtk# provides a C source parser and C# code generator that can be used to produce .NET assemblies that bind to GNU object libraries.

Mainsoft technology comes into play when IT organizations want to cross-compile .NET Web and server applications to run on established Java EE application servers. The ability to deploy applications across platforms provides software vendors with access to a wider market for their products. SourceGear uses both Mono and Mainsoft software to provide Vault, the company's source code control software, on Unix systems. OTEE uses Mono for its Unity Game development engine. VistaDB uses Mono to provide its VistaDB embedded SQL database engine across multiple platforms. And Segway Software uses Mainsoft's software to deliver a tight integration between its Segway Sales Productivity Suite, written entirely in Microsoft .NET, and a customer's existing pricing management and configuration system written in Java. There are dozens of other success stories for cross-platform porting and support using cross-platform development tools.

Open Source .NET and the Future
It is important for those considering using cross-platform technologies that they are stable and reliable, and have ongoing road maps to let developers know when new technologies will become available.

The Mono project already has projects implementing several upcoming technologies that fall under .NET 3.0. One subproject, Olive, is implementing CardSpace, Windows Communication Foundation (formerly known as Indigo), and Windows Workflow Foundation. Other .NET 3.0 technologies, such as the Windows Presentation Foundation, a new API for creating desktop applications, are not on the current Mono roadmap.

A second subproject, Crimson, implements technologies that have not been addressed as ECMA/.NET standards by Microsoft, but that Mono considers important for applications running on multiple platforms using Linux.

Mainsoft is also committed to ensuring compatibility with future releases of the .NET Framework, as well as with future Java releases. The next release will incorporate the ability to use Visual Studio 2005 and the .NET Framework 2.0 in building ASP.NET and .NET server applications. Beyond that, its software will pick up the Mono libraries to support .NET Framework 3.0 features such as Windows Communication Foundation and Window Workflow Foundation. A Grasshopper 2.0 Technology Preview is currently available at http://dev.mainsoft.com.

Sidebar:

Use the Visual Studio .NET IDE and Grasshopper for Linux
We all know the Microsoft Visual Studio .NET IDE, but did you know that you can use it to build server applications that run on Linux? Discover how, with Visual MainWin for J2EE from Mainsoft, Visual Studio users can run their applications natively on J2EE and Linux environments.

Take a look at Figure 1. It's clearly an ASP.NET application, and it's clearly running on Linux. That's easy, you might think, you can build an ASP.NET application, run it on Microsoft Windows under Internet Information Services (IIS) and browse to it using a browser such as Firefox on a Linux client. You'd be right, but look again. In the screen shot, your ASPX is running on localhost, the Linux box itself. With Visual MainWin for J2EE, also known as Grasshopper, you can do this easily, without changing your existing .NET code. Therefore, you can say that Visual Studio .NET + Grasshopper = Visual Studio .NET for Linux!

Extending your skill sets to Linux
Consider this - many companies have Linux on their radar for some form of inclusion in their strategy, be it on the desktop or in the data center. To build applications for Linux, you would probably have to learn a new skill set such as GTK or Java. For server side or hosted applications, the logical candidate is usually J2EE, due to its cross-platform nature and its well-known security, manageability, performance and scalability characteristics. However, to develop J2EE applications, you need to learn the Java language, Java Servlets, Java Server Pages, JDBC for database connection and even Enterprise Java Beans for distributed applications. What if, as an alternative, you could broaden the reach of your skills to Linux and other Java-enabled platforms, and as a result, extend yourself (and your resume) in a new and exciting area? What if you could do this without rewriting most of your code, and instead re-use your existing C# code? Not only that, but would you like to contribute to the Mono project - the creation of an open source .NET Framework for Linux? Well you can, and you can do it today, with Grasshopper, a freely available download from Mainsoft.