Xamarin.Forms device unique ID...

As in a lot of applications, you will probably need to get a unique identifier to identify a unique user.
And it becomes a little more complicated when you have to deal with different platforms like Android, iOS and Windows Phone...

Here is a simple solution that you can implement in Xamarin Forms that I found on this blog:
http://codeworks.it/blog/?p=260


First define a service that you will use in your Xamarin Forms Application:

// Your service interface definition
public interface IDevice
{
   string GetIdentifier();  
}

// How you get your service in your app
IDevice device = DependencyService.Get();
string deviceIdentifier = device.GetIdentifier();

And here are the implementations for Android / Windows Phone and the most complicated, iOS platform:

// WINDOWS PHONE
[assembly: Xamarin.Forms.Dependency(typeof(WinPhoneDevice))]
namespace XFUniqueIdentifier.WinPhone
{
 public class WinPhoneDevice : IDevice
 {
  public string GetIdentifier()
  {
   byte[] myDeviceId = (byte[])Microsoft.Phone.Info.DeviceExtendedProperties.GetValue("DeviceUniqueId");
   return Convert.ToBase64String(myDeviceId);
  }
 }
}

// ANDROID
[assembly: Xamarin.Forms.Dependency(typeof(AndroidDevice))]
namespace XFUniqueIdentifier.Droid
{
 public class AndroidDevice : IDevice
 {
  public string GetIdentifier()
  {
   return Settings.Secure.GetString(Forms.Context.ContentResolver, Settings.Secure.AndroidId);
  }
 }
}

// iOS
//
[assembly: Xamarin.Forms.Dependency(typeof(IOSDevice))]
namespace XFUniqueIdentifier.iOS
{
 using System.IO;
 using System.Runtime.InteropServices;

 public class IOSDevice : IDevice
 {
  [DllImport("/System/Library/Frameworks/IOKit.framework/IOKit")]
  private static extern uint IOServiceGetMatchingService(uint masterPort, IntPtr matching);

  [DllImport("/System/Library/Frameworks/IOKit.framework/IOKit")]
  private static extern IntPtr IOServiceMatching(string s);

  [DllImport("/System/Library/Frameworks/IOKit.framework/IOKit")]
  private static extern IntPtr IORegistryEntryCreateCFProperty(uint entry, IntPtr key, IntPtr allocator, uint options);

  [DllImport("/System/Library/Frameworks/IOKit.framework/IOKit")]
  private static extern int IOObjectRelease(uint o);

  public string GetIdentifier()
  {
   string serial = string.Empty;
   uint platformExpert = IOServiceGetMatchingService(0, IOServiceMatching("IOPlatformExpertDevice"));
   if (platformExpert != 0)
   {
    NSString key = (NSString) "IOPlatformSerialNumber";
    IntPtr serialNumber = IORegistryEntryCreateCFProperty(platformExpert, key.Handle, IntPtr.Zero, 0);
    if (serialNumber != IntPtr.Zero)
    {
     serial = NSString.FromHandle(serialNumber);
    }

    IOObjectRelease(platformExpert);
   }

   return serial;
  }  
}

Original post:
http://codeworks.it/blog/?p=260