Many years ago, in fact pre-Java, I remember a hallway discussion about the desire to write a single application that could easily run across various platforms. At the time, we were only worried about writing applications on Windows 3.1 and Mac OS 7.x. There were many discussions about windows, user interface concepts, and specifically a rather long discussion as to whether Mac users would accept a Mac application that didn't have balloon help. Thankfully, the marketplace answered this question for us with the Windows API winning the battle.

A similar set of questions is currently going on in the mobile world. Unfortunately, at this point in time, there is currently no winning API and none currently in sight. What's a developer to do? Here are some questions that developers have (and there are many more):

• How can mobile developers target Android and the iPhone with the same code?
• How can .NET developers share their code across Android, iPhone and other platforms?
• How can developers give applications the look and feel of the specific platform and still allow as much code as possible to be shared?
• Mobile devices share many common features, such as cameras, accelerometers, and address books. How can we take advantage of them in a platform independent way and still give the users the look of every other application running on their platform?

In this article, we'll look at some solutions to these cross-platform and code-sharing questions between Mono for Android, MonoTouch and the .NET Framework available to developers.