gistfile1.cs

1. [JournalViewController.cs]
NSNotificationCenter.DefaultCenter.AddObserver (this, new Selector ("updateJournal"), UIApplication.DidBecomeActiveNotification, null);
//Should replace with:
UIApplication.Notifications.ObserveDidBecomeActive (handler);

2. [JournalViewController.cs]
var components = new NSDateComponents ();
components.Day = calendar.GetComponentFromDate (NSCalendarUnit.Day, now);
components.Month = calendar.GetComponentFromDate (NSCalendarUnit.Month, now);
components.Year = calendar.GetComponentFromDate (NSCalendarUnit.Year, now);

var startDate = calendar.DateFromComponents (components);
var endDate = calendar.DateByAddingUnit (NSCalendarUnit.Day, 1, startDate, NSCalendarOptions.None);

var predicate = HKQuery.GetPredicateForSamples (startDate, endDate, HKQueryOptions.None);

// This arithmetic should be replace with .Net equivalent:
var startDate = DateTime.Now.Date;
var endDate = startDate.AddDays(1);
var predicate = HKQuery.GetPredicateForSamples ((NSDate)startDate, (NSDate)endDate, HKQueryOptions.None);

3. [EnergyViewController.cs]
RefreshControl.AddTarget (this, new Selector ("refreshStatistics"), UIControlEvent.ValueChanged);

// Should be replaced with event
RefreshControl.ValueChanged += RefreshStatistics;

4. [EnergyViewController.cs]
NSNotificationCenter.DefaultCenter.AddObserver (this, new Selector ("refreshStatistics"), UIApplication.DidBecomeActiveNotification, null);
// Should be replaced with Strongly type equivalent:
UIApplication.Notifications.ObserveDidBecomeActive (handler);

5. [EnergyViewController.cs]
// Calendar arithmetic should be replace with .Net equivalent:

6. [AppDelegate.cs]
// Why it is public? As I can see it used only inside AppDelegate.cs and then injects to other controllers
// maybe it should be replaced with private field?
public static HKHealthStore HealthStore { get; private set; }

7. [AppDelegate.cs]
// error message is broken – %@ must be replaced with {0} and error must be provided as second argument
Console.WriteLine ("You didn't allow HealthKit to access these read/write data types. " +
"In your app, try to handle this error gracefully when a user decides not to provide access. " +
"The error was: %@. If you're using a simulator, try it on a device.");

8. [AppDelegate.cs]
foreach (UINavigationController navigationController in tabBarController.ViewControllers) {
	var viewController = navigationController.TopViewController;

	if (viewController is ProfileViewController)
		(viewController as ProfileViewController).HealthStore = HealthStore;
	else if (viewController is JournalViewController)
		(viewController as JournalViewController).HealthStore = HealthStore;
	else if (viewController is EnergyViewController)
		(viewController as EnergyViewController).HealthStore = HealthStore;
}

// Declare IHealthStore interface which contains just one property HealthStore.
// ProfileViewController must implement this interface. After that replace code above with:
foreach (UINavigationController navigationController in tabBarController.ViewControllers) {
	IHealthStore controller = navigationController.TopViewController as IHealthStore;
	if(controller != null)
		controller.HealthStore = HealthStore;
}

9. [AppDelegate.cs] // this topic just my pref
HealthStore.RequestAuthorizationToShare (writeDataTypes, readDataTypes, (success, error) => {
	if (!success) {
		Console.WriteLine ("super important message");
	} else {
		SetupHealthStoreForTabBarControllers ();
	}
}

// I think it more beautifully because it is branchless (easily to understand)
HealthStore.RequestAuthorizationToShare (writeDataTypes, readDataTypes, (success, error) => {
	if (!success) {
		Console.WriteLine ("super important message");
		return;
	}
	
	SetupHealthStoreForTabBarControllers ();
}