This is a really quick and easy tip for those starting out doing iOS development with Xamarin (and specifically with the Visual Studio extensions). If you don’t have access to an iOS device and want to debug on the Simulator that ships with Xcode make sure you do the following:
Set the “Platform” to “iPhoneSimulator” for the project.
1. Select the Solutions Configuration menu (allows you typically to choose Debug or Release) and is next to the “Start” debug button.
2. In the Configuration Manager for your iOS App select “Platform” and change to “iPhoneSimulator” (highlighted below).
3. Save the changes and you should now be able to debug.
I scratched my head on this for a while ;).
BTW, did I say how cool it is that you can develop Android and iOS apps from right inside Visual Studio? You still need a Mac and Xcode for iOS but Android is there for the taking (you can even edit the axml layout files directly inside Visual Studio!)