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Mono is an open source development platform based on the
.NET Framework. This platform increases your options by providing a vehicle for
developing Windows applications, as well as OS X and the many flavors of
UNIX/Linux.

What is Mono?

Mono is based on the fact that the C# language and the CLI
(Command Language Infrastructure) have been accepted as standards by ECMA.

The Mono libraries include .NET compatibility libraries (including
ADO.NET, System.Windows.Forms, and ASP.NET) and
Mono-specific third-party class libraries. It’s also possible to embed Mono’s runtime into applications for simplified packaging
and shipping. In addition, the Mono project offers an
IDE, a debugger, and a documentation browser.

How to install Mono

Mono is freely available from the project’s Web site, with
downloads available for Linux (a generic installation, SUSE, and Red Hat), Windows,
and OS X. You can download the complete source code and compile it (which is
the only choice if your platform isn’t supported) or download the appropriate
installation package. We’ll stick to the installation package route in this
article.

Once you download the appropriate package for your platform,
the installation process varies by operating system. Currently, I have Mono
running on Windows XP and SUSE Linux 9.2 machines. The Windows installation is
as simple as downloading the installation package and running it on your
machine, whereas the other distributions are not as easy.

The Linux installations include individual files for the
various aspects of the Mono platform. Here is a sample of the parts of Mono
available for download for SUSE:

  • mono-devel-1.0.6-1.ximian.9.1.i586.rpm—Mono
    core package with C# compiler
  • mono-core-1.0.6-1.ximian.9.1.i586.rpm—Mono
    core runtime
  • mono-data-1.0.6-1.ximian.9.1.i586.rpm—Database
    core

Each file in the list is a RPM (Red Hat Package Manager)
file. You may install these files on the Linux box with the rpm command-line
tool. For example, you can install the core Mono runtime with the following
command:

rpm – i mono-core-1.0.6-1.ximian.9.1.i586.rpm

After installing Mono, you should add it to your system’s
path so you can easily issue commands without specifying the complete path. You
can do this via the Window’s control panel or using the export PATH command on
Linux.

Tip: If you’re
experiencing any Mono installation problems at this point, I recommend visiting
the Got Mono? Web site for excellent install troubleshooting tips.

The Mono toolset

Once you install Mono, you may utilize its various tools.
Here’s a look at some of these tools:

  • mono—The mono interpreter that allows for the execution
    of applications without using JIT. This allows you to run applications
    from the command line. There is no corresponding tool in the Microsoft
    .NET Framework.
  • mcs—The
    C# compiler that accepts all the same command line options that the
    Microsoft C# compiler (csc.exe) does.
  • monodies—A tool that allows you to disassemble
    applications into IL (Intermediate Language). It provides functionality
    similar to Microsoft’s ildasm.exe.

Please refer to the Mono documentation for a more complete
list of tools, along with a discussion of each command’s options.

Build a Mono application

Now we’ll build a simple Mono application to see how to use a
few of these tools. The following code prints a sample message to the console:

using System;

namespace Builder.Samples {

public class MonoDemo {

public static void Main(string[] args) {
Console.WriteLine("Check out TechRepublic.com");

} } }

We’ll save this simple example as MonoDemo.cs,
which may be compiled with Mono’s C# compiler:

mcsMonoDemo.cs

The result of the compilation is the file MonoDemo.exe. The
.exe file extension is common on a Windows system, but it is an odd occurrence
on a Linux system. Therefore, we’ll run our example with this command-line
interpreter:

mono MonoDemo.exe

The great aspect of this example is that we may run the
compiled file on a Windows, Linux, Mac OS X, or any platform running Mono or
the Windows .NET Framework. This is because the Mono compiler compiles code
into an intermediary form known as IL.

The Microsoft C# compiler does the same thing. However, Mono
doesn’t have a complete implementation of the .NET class libraries; it does
have additional Mono-specific libraries. Consequently, not all applications
developed with Mono can be run in the Microsoft .NET Framework and vice versa.

You will have to take this into consideration during
development by understanding the target platforms and future demands for
compatibility. Likewise, you should visit the Mono site frequently to stay
up-to-date with the project since new features (like class libraries) are continuously
being added. This is true on the Microsoft side as well.

Concerns

While I love the ability to transfer my C# knowledge from
the Windows platform to the many flavors of Linux and other platforms, I am
hesitant about full-blown .NET development on anything but Windows. Basically,
Microsoft donated the C# language as well as the CLI to the community but other
technologies like ADO.NET and ASP.NET were not submitted. This makes me wonder
if Microsoft will make a move to squash the ASP.NET and ADO.NET engines
currently available in Mono. Applications hosted on Web servers other than IIS
and Windows hurt Microsoft’s bottom line.

This may be my paranoia, but it is something I will keep an
eye on. One last issue is the lack of support for non-C# languages; this leaves
VB.NET programmers in the cold.

Dive in

The Mono project is an impressive feat accomplished within
the open source framework. It supports many features of the .NET Framework,
with 2.0 features currently supported or in the process of being supported. In
addition, Mono’s specific libraries for developing
Linux-based applications (the gnome interface) are a boost for Linux
development. Mono is a good reason for Windows developers to take a peek at
Linux.