Can I develop iPhone applications using C#.NET on Vista?

Question

I’m interested in developing an iPhone application using Visual Studio and C#.NET on Windows Vista.

I tried to download the SDK from http://developer.apple.com/iphone

Answer 1

UPDATE 7/18/2013:

Since this answer is 3 years old I would like to update it with current information. MonoTouch is no more because it is now part of Xamarin. With it you can develop mobile applications using C# and parts of the .NET Framework (using Mono). You can develop iOS apps using Windows and Visual Studio, but you still need a Mac to compile and build. Here's a blog post on how to use VS for iOS development.

ORIGINAL ANSWER

MonoTouch. You still need a mac and a minimum of $400 (as of this writing)

You can try the eval version which doesn't require you to pay and allows you program using the simulator. If you want to test your app on the hardware then you need to pocket the money.