You haven't mentioned anything about what the app is supposed to do, your skill set, what tools you intend to develop the app with etc.
At the very least do some initial research, see how far you get, and then (and only then) post a specific question when you need some help.
"There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies. The first method is far more difficult." - C.A.R. Hoare
There is no single unified IDE for both mobile platforms unless you are considering cross platform development. In which case I would highly recommend Xamarin. A good introductory article (written by me) can be found here Introduction to Xamarin.Android[^]
How i can download from ftp server specific file in Windows Mobile (C#).I Have ftp link,username and password. i want only download. I dont want use non standart compenents. (OpenNETCF dll returned error codes)
I'm not overly familiar with Windows Mobile but to my knowledge there aren't any native FTP clients. You can of course write your own if you don't want to use a third-party component. I wrote my own FTP client a while ago when I needed an FTP client for my .NET applications.
Good day friends. I want to start writing applications that can run on nokia mobile phones irrespective of the os and I don't know where to get the software because i have searched and couldn't found any. Please does anyone know where i can download it from? Thanks in advance.