This recipe shows how to make various environment checks from your code to handle different runtime environments.

You can detect whether you are running on the simulator or device by looking up the value of the ObjCRuntime.Runtime.Arch field. If the value is ARCH.Device, you are running on the physical hardware, otherwise you are running on the simulator.

The iOS and tvOS operating system version can be checked like this:

if (UIDevice.CurrentDevice.CheckSystemVersion (9,0))
{
   // Code that uses features from iOS 9.0 and later
} else {
   // Code to support earlier iOS versions
}

the UIDevice class exposes other environment properties that can be checked.

The watchOS operating system version can be checked like this:

if (WKInterfaceDevice.CurrentDevice.CheckSystemVersion (3, 0)) {
// Code that uses features from watchOS 9.0 and later
} else {
// Code to support earlier watchOS versions
}

The version of Xamarin.iOS is stored in the field ObjCRuntime.Constants.Version. This is a string, you can turn this into a Version object with code like this:

Version version = new Version (ObjCRuntime.Constants.Version);
if (version > new Version (7,0))
{
   // Code that uses features from Xamarin.iOS 7.0
}