How could I create iPhone applications using the .NET development environment?
As far as I know, Apple does not support the Microsoft .Net development environment.
At most you could hope for is installing mono on a jailbroken iphone. Not that I condone this and you do so at your own risk.
IPhone applications are developed using Objective C or Ruby.
You don't. You need Xcode on Mac OS X to write iPhone applications.
Update: 9-20-2009
This was once true. See comments below for more info.
The Mono team are working on 'static compilation' which allows mono apps to be run on a non-jailbroken iPhone. In short this works by running a cross-compiling JIT step as part of the build process to generate a native exe.
There was a demo of this at the PDC ... see Miguel de Icaza's blog.
The only supported way to develop native iPhone applications is the iPhone SDK. It runs on Mac OS X only, and supports development using the Cocoa Touch frameworks and the Objective-C 2.0 language.
If you just want to leverage some knowledge of c#, you can use Unity. Games developed with Unity (http://unity3d.com) use Mono with an AOT (ahead-of-time compiler) to compile mono bytecodes to ARM. (The apps created by Unity have a shell that is, in fact, a fairly conventional cocoa touch app created in Objective-C++ and XCode.) It's not a dot net app, but you can use your existing knowledge of c#.
There are ways to get other languages to work, they will - however - almost certainly not be accepted to the AppStore and will break with future updates. Generally it is better to use a screw driver to screw something into a hole than to thwap it repeated with a hammer attached to a 250hp motor...
The answer is MonoTouch From Novell - http://www.mono-project.com/MonoTouch. Beta version will be released on August 2009 and commercial released will be on September 2009.
You can use Third party Tool called Component Studio - iPhone . More info please refer below url http://www.componentone.com/SuperProducts/StudioiPhone/
Netaji B Sapkal