Visual Studio 2010 is in the market for a little while. That sounds like no opensource alternative for .Net 4.0 until now. SharpDevelop 4.0 Beta 1 is released. I have tried that. So far, my first impression is slower. I guess that is because the UI is heavy rewritten in WPF. I think most of people will agree WPF got a better appearance and runs slower. But it got a feature I want for long time. Windows forms designer for WPF. Now, you can use the form desginer to edit xaml. That's great! By the way, in release notes, they do not recommend to use the form designer for editing .net 2.0 winfrom files. I tried that, so far, I have not faced any major issues. Well, they don't recommend that, I think you should not do that.
Lastly, so far, I am very happy to the new version. It looks better and got more features!
I found that actually you can develop iPhone app in C#. There is an application from Novell, MonoTouch. I read the documentations, it seems to be directly interface with the native iPhone OS. That sounds quite nice and it supports iPhone OS. Although it sounds powerful, it is not a freeware. Even the professional edition costs $399!
The 2nd day of keynote is about Android. Mainly, Google presented the newest version of Android, 2.2. They is a faster OS. Moreover, the Android market has some new features, such as "Update All". You can click "Update All" button to update all applications in your phone, rather than updating them one by one. But sadly, the payment processor for Android Market is still only available for developers in the limited locations to sell their apps.
Setting the Icon of a window in WPF is very simple! In your window xaml, you need to put the filename of your icon file in icon attribute, like the following:
Moreover, please the properties in the icon file. The build action sets to be "Content" and Copy to output directory sets to "Always".