Prism for Xamarin Forms Preview 3

So much goes into developing a Xamarin Forms application, and Prism for Xamarin Forms is continuing to make your mobile development a little easier. Today we released Preview 3 for Prism 7, and a lot has happened since I published the Sneak Peak and the changes to Autofac.

 

Navigation

One of the big things developers love about Prism is Deep Linking like "NavigationPage/ViewA/ViewB/ViewC". Unfortunately this also exposes a bug in Xamarin Forms which the Xamarin team hasn't fixed. The result has been that the Title displayed in the NavigationPage is for ViewA rather than ViewC. Prism 7 has finally fixed this issue so that deep linking can still occur properly.

A long awaited feature is Relative Navigation. We see this all the time in web development, and beginning with preview 3 you can now simplify our Navigation like "../SomePage". This will both pop the current page and add SomePage to the Navigation Stack. Keep in mind that this feature will only work within the context of a NavigationPage. 

Another long await feature has been the ability to simply go back to the root. Prism's Navigation Service now includes a GoBackToRootAsync extension that will support this exact use case. 

TabbedPages

Prism 7 has a lot of fixes to make working with TabbedPages a joy. In past versions of Prism we've had to both explicitly set the ViewModelLocator.AutowireViewModel property on any pages that will be children of a TabbedPage, and we've had to create a TabbedPage that explicitly sets the tabs.

<?xml version="1.0" encoding="UTF-8"?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
            xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
            xmlns:local="clr-namespace:AwesomeApp.Views;assembly=AwesomeApp"
            x:Class="AwesomeApp.Views.MyTabbedPage">

    <local:ViewA />
    <local:ViewB />
    <local:ViewC />

</TabbedPage>

Beginning with Prism 7 you can now simply register the Xamarin Forms TabbedPage for Navigation and simply navigate like "TabbedPage?createTab=ViewA&createTab=ViewB&createTab=ViewC". But it doesn't stop there. There are times that we want to use a NavigationPage for a particular tab. We can now easily do this by adding the pipe character and navigating like: "TabbedPage?createTab=ViewA&createTab=NavigationPage|ViewB&createTab=ViewC". Best of all is that the NavigationService now better handles the children so that whether you have a traditional TabbedPage like above or one generated from the querytstring your pages will be automatically get the ViewModelLocator.AutowireViewModel set, and any Prism Behaviors will also automatically be set.

There has also been a major breaking change for selecting the active tab. In previous versions of Prism for Xamarin Forms you could set the active tab by adding the tab to select as the next Uri segment "MyTabbedPage/ViewB". This has been changed in preference of a querystring parameter like "TabbedPage?selectedTab=ViewB". Note that for those who are concerned about magic strings, we've got you covered as this is all based on the constants in KnownNavigationParameters. Putting this all together you can now navigate like:

_navigationService.NavigateAsync($"TabbedPage?{KnownNavigationParameters.CreateTab}=ViewA&{KnownNavigationParameters.CreateTab}=ViewB&{KnownNavigationParameters.CreateTab}=ViewC&{KnownNavigationParameters.SelectedTab}=ViewC");

Lifecycle

IActiveAware has been around Prism for some time but has only had limited support to handle when a page becomes the current page inside of a TabbedPage or CarouselPage. A new interface has been added to Prism.Forms called IPageLifecycleAware. This is handled through a Behavior added to every page by the NavigationService which will allow you to respond to the Appearing and Disappearing events.

Sticking with being Lifecycle aware, preview 3 has introduced a breaking change from earlier previews with IApplicationLifecycle to IApplicationLifecycleAware. While there hasn't been any actual changes to the way it works, it does better fit the naming conventions in Prism.

Modularity

Modularity has long been a core concept in Prism. Modularity has gotten a whole lot nicer in Prism 7 with a few fixes. To start with IModuleCatalog was fixed to properly return IModuleCatalog rather than ModuleCatalog when adding a Module. One of the problems with adding Modules in previous versions has been the verbosity that was required:

ModuleCatalog.AddModule(new ModuleInfo(nameof(SomeModule), typeof(SomeModule), InitializationMode.WhenAvailable));

This can now be simplified like:

// Basic Registration
ModuleCatalog.AddModule<SomeModule>();

There are of course some overloads to specify either the name or Initialization Mode. We have also added extensions to better determine whether a Module has been added to the ModuleCatalog and what the ModuleState is.

 

Xamarin Forms UI Development Made Easy with LiveXAML

I'm all about working with XAML in my Xamarin Forms apps. Developers coming from a WPF background have been used to some great tooling for visually styling their XAML for years. Xamarin Forms of course isn't so cut and dry for the obvious reason that we're dealing with an Abstraction of the UI. Chances are you've probably heard about Xamarin's Live Player. To be honest I think it's a cute idea, but really lacks what you need to be most productive. 

Naturally one of the biggest pains when working with XAML is getting the Styling just right. We do have more tools now at our disposal like the XAML Previewer in Visual Studio and Visual Studio Mac, but it lacks the touch and feel component of styling. This is where LiveXAML is making a huge difference in developing Xamarin Forms applications. LiveXAML not to be confused with Xamarin's Live Player, allows you to get the updates directly in your actual app. LiveXAML is truly one of the most amazing products I've ever worked with for XAML. 

It really is as simple as installing a single NuGet package and running the application in your Simulator or on your Device. Now you can actually see what your changes are doing, without rebuilding, in an app that is fully functional. There are no short cuts, no limitations like we see with the Live Player or the Previewer.

There are a number of challenges that are hard to handle without a data context behind them. One of them is handling a ListView with a DataTemplateSelector. It's certainly one thing to refine a single ViewCell, but when you have multiple cells that each need to be styled there is no substitute for having real working data which can only happen with your app actually running. This is one the many scenarios where using LiveXAML can really shine as you quickly update the styling and see the changes in your app. 

If you haven't had a chance to check it out head over to http://livexaml.com

Prism Template Pack in Visual Studio for Mac

Prism users have long enjoyed some great Template packs available for Visual Studio and Xamarin Studio. Visual Studio for Mac though has been a real challenge due to problems with the Mono Addins site not building the Prism Addin. It's been a very common request among our Mac users to get this support back.

Since we have been unable to rely on the Mono Addins site, we have decided to simply host our own feed for Prism Users. This new feed will allow you to add and update the Prism Template Pack in Visual Studio for Mac.

So how do you get the Template Pack? Well for starters you will need to add the Prism feed to your Extensions Repositories. Once you have it added, simply refresh the Gallery. You can either use the search bar or expand IDE extensions to find the Prism Template Pack.

Keep in mind that the new Prism Template Pack for Visual Studio for Mac now includes a DryIoc Project template in addition to the Unity Template. Both project templates will create project with the latest stable versions of Prism and Xamarin Forms.

Breaking Changes for Prism Autofac Users

History

It's certainly been no secret that I've told user's that Autofac wasn't really a good choice for Prism Forms. To be honest just looking at the benchmarks between Autofac and DryIoc or SimpleInjector which may soon be supported, Autofac just isn't that appealing to me. The truth though, is that I wasn't just steering people away from Prism Autofac for this reason alone.

Before Prism introduced .NET Standard support, we were limited to targeting Autofac 3.5. As anyone familiar with Autofac is likely aware, the ContainerBuilder.Update(Container) method was deprecated. Autofac quite annoyingly wants to be an immutable container. This is problematic for frameworks like Prism, or any developer who wants to dynamically load dependencies (more on this later). Also part of the problem was that Autofac is a bit unique in the way that it handles registering and resolving. Most containers are responsible for registering dependencies, telling you if something is registered, and resolving that dependency, but Autofac wants to be different with a ContainerBuilder that is used for registering, a central IContainer that knows nothing about itself, but is happy to resolve IComponentContext if you need to inject something into a class to resolve dependencies in a factory method like the one used by the NavigationService to resolve your Views... 

Major Breaking Changes

Prism Forms is architected for a Container that knows how to do stuff, continuing to have the Autofac PrismApplication derive from PrismApplicationBase<IContainer> was a poor choice. To help fix the way Autofac works with Prism Forms this was updated to PrismApplicationBase<ContainerBuilder>. That alone though would provide for a poor experience so this was updated to ensure that the Container property is still the IContainer that is set when the builder is built, and a Builder property was added to give you direct access to the ContainerBuilder being used in PrismApplication to register all of the Prism services. Unlike the builder previously used by PrismApplication, this builder waits to call Builder.Build() until after it registers the base Prism services, anything in your RegisterTypes() and anything in your IPlatformInitializer.

To make this work though, we also had to break all of your View Registrations. The extension methods that we typically include in Prism Forms are based on the Container for registrations. But this never made sense for Autofac, leading to extension methods that would create a builder, and then update the Container. To better align with the intent of how Autofac is meant to work the methods were updated to be based on the ContainerBuilder.

public class App : PrismApplication
{
    protected override void RegisterTypes()
    {
        Builder.RegisterType<Foo>().As<IFoo>();
        Builder.RegisterTypeForNavigation<ViewA>();
    }
}

public class iOSInitializer : IPlatformInitializer
{
    public void RegisterTypes(ContainerBuilder builder)
    {
         builder.RegisterType<SpeakImp>().As<ISpeak>();
    }
}

Modularity

Modularity hasn't been huge in the Prism Forms community like it is in the WPF community. For developers who are familiar with it, Modules are often a major part of their app development. Unfortunately Autofac's desire to be immutable poses some major problems for Modularity with Prism. Prism relies on container mutability for Modules. Part of this is that we must resolve the ModuleCatalog before we run it and initialize any of the Modules. The other part is that Prism allows us to load Modules on demand. This could for instance allow us to ship an application like Lyft and only load the Driver Module if the user is a Driver. Since Autofac is immutable this creates a major problem for us, and OnDemand Modules are out of the question due to the limitations imposed on us by the container. As such the recommended guidance for Autofac users will be to architect modules as follows:

public class AwesomeModule : IModule
{
    public void Initialize() { }

    public static void Initialize(ContainerBuilder builder)
    {
        builder.RegisterType<FooService>().As<IFooService>();
        builder.RegisterTypeForNavigation<ViewA>();
    }
}

public class App : PrismApplication
{
    protected override void RegisterTypes()
    {
        // Initialization must be done before the Container is built.
        AwesomeModule.Initialize(Builder);
    }

    protected override void ConfigureModuleCatalog()
    {
        // Not actually needed for Autofac since all registrations must be done
        // before we build the container.
    }
}

Getting Started

These changes are all available starting with Prism 7.0.0.30-ci in the Prism MyGet feed. If you have not already done so, you can add that feed in either Visual Studio or Visual Studio for Mac and update your existing Prism Application's to the latest CI build. 

If you are starting with a new Project you will want to check out the updated QuickStart Templates which now includes the only Module project template, and full support for the updated Autofac implementation.

Prism 7.0 for Xamarin Forms Sneak Peek

Prism 7.0 Sneak Peek

If you're a Xamarin developer, chances are you've been through a struggle or two with NetStandard. NetStandard offers a lot of advantages, but support has been slow going in many cases. Xamarin Forms only recently began shipping NetStandard. Prism users have been asking for a while now to have NetStandard support. Obviously for WPF users NetStandard really doesn't offer any advantages, and for UWP it just creates a few headaches, but that hasn't stopped requests for the Core to support NetStandard or for Prism Forms to be converted. For a while now I've been either pointing people to my preview templates or telling them to use the PackageTargetFallback attribute with the new csproj format. Well, I'm happy to say that Prism for Xamarin Forms is now available in NetStandard!

While NetStandard support is fantastic, I probably wouldn't take the time to write a post just about that. One of the problems we all face is when we run into an issue with a library in our code base, and the issue is fixed on GitHub. The problem is that it may be days, weeks, even months before it is available. So suddenly you have to uninstall the NuGet packages, add the open source library as a git submodule. As Prism moves into the 7.0 update, I'm also very happy to announce the official Prism MyGet feed that is tied into the builds so when new features are added you can immediately expect a new CI package available on MyGet so you can immediately start using the features you need without having to wait for an official release. 

https://www.myget.org/F/prism/api/v3/index.json

Whats New Since 6.3

You may be thinking that NetStandard is great and all but that isn't really new. As part of Prism updating to Xamarin Forms 2.3.5, you will now have full support for working with Prism on macOS applications. 

Another change you can look for starting now in the 7.0 addresses the overhauled OnPlatform starting in Xamarin Forms 2.3.4. Unfortunately the new Xamarin API for OnPlatform uses magic strings, and is cumbersome to say the least if you're working with it from C# code and not in XAML. Prism has updated the IDeviceService and provided a new RuntimePlatform enum. We have also updated Platform dependent View Registrations to use this new RuntimePlatform enum. This will ultimately be a lot cleaner than the previous type based registrations.

Container.RegisterTypeForNavigationOnPlatform<MainPage, MainPageViewModel>("Main",
     new Platform<MainPage_Android>(RuntimePlatform.Android),
     new Platform<MainPage_iOS>(RuntimePlatform.iOS));

Following the deprecation of the previous OnPlatform functions within the Xamarin Forms Device class, we have updated IDevice to deprecate this feature as well and added access both the Xamarin Forms Platform string and our RuntimePlatform enum.

I have been a huge advocate for directly binding to your model's properties. It really saves a lot of headaches with validation and ensuring that changes made on the view update your model to be persisted to your data store. That said even with Prism's DelegateCommand.ObservesProperty, this has been a shortcoming. Thanks to a community contribution this will now be possible in Prism 7.0

ObservesProperty(() => Property.NestedProperty.NestedPoperty)

Another major improvement addresses exceptions thrown during navigation. Prism Forms will now properly log and re-throw exceptions that are thrown when you're navigating. This has been a major pain point in the past where the exceptions were effectively swallowed by the NavigationService and you had no idea what threw an exception or even what the exception was. Many times you might have simply found yourself getting an exception thrown because your MainPage was null and the platform excepted something. 

There have also been a number of reported Navigation Bugs fixed in Prism 7.

Prism for UWP Developers

If you're developing UWP applications with Prism there are a couple of gotcha's that you'll need to know about. 

Starting in Prism 7.0 we've decided to split all of the Platforms/Containers into separate packages. We've done this so that we can rev the platforms separately from one another, and if we update an issue with Prism.Autofac.Wpf, Prism.Autofac.Windows user's won't see a package update and think that something changed. This only affects UWP developers who are using Prism for UWP. You simply need to uninstall the Prism.{Container} package and install the Prism.{Container}.Windows package. (note that this update is not yet available but will be soon)

Whether you're using Prism for UWP or Prism for Xamarin Forms, note that there is a bug with the .NET SDK that will affect you if Prism 7 is the first NetStandard package that you are using. It is easily overcome by adding the file Directory.Build.props next to your solution file, with the following contents:

<?xml version="1.0" encoding="utf-8"?>
<Project>
  <!-- Workaround for https://github.com/dotnet/sdk/pull/908 -->
  <Target Name="GetPackagingOutputs" />
</Project>

Note that if you are developing a UWP application with the Prism QuickStart Template for Xamarin Forms, this has already been added for you.

Whats Coming

As amazing as NetStandard is to finally have behind us, I'm still even more excited by what's coming in 7.0. I wouldn't call this an exhaustive list, but here are some highlights of some features to keep an eye out for in Prism 7:

  • Querystring navigation is one of the most amazing things about the Prism Navigation Service, and it's about time that you should be able to dynamically create tabs or use modal navigation through the querystring.
  • Removal of support for the Xamarin Forms DependencyService. This really leads to some bad practices, and with IPlatformInitializer there is simply no need to rely on the Dependency Service for Platform specific types.
  • An ability to use MVVM and the ViewModelLocator with custom Views as well as Xamarin Forms Pages.

 

Prism Quickstart Templates

Quickstart Templates for Prism Forms

So you had this great idea for an app... maybe you spent weeks planning with your team or with your client. The day finally comes to create the project. Suddenly you realize that we have this new .NET Standard thing and you want to take advantage of that too. You remember you need icons, you want a Splash Screen... all of the things that go into making an App. For anyone who has done this, you know there's a lot of heavy lifting to be done. In all honesty you could easily spend several days just getting a new project from File -> New to something that you're ready to start working on.

It was for this and so many other reasons that I realized we need better templates, and we need something that can help us whether we're on a Mac or on PC.

There are some very basic things left out of the base Xamarin & Prism Templates. For some developers these just require time that could be better spent on something else, and for other developers it leads them down a path of poor design.

Features

Why should you use these templates? Well here are a couple bullet points:

  • Gets you off the ground following Best Practices
  • *Starts you off using Prism for Xamarin Forms with either DryIoc or Unity for Dependency Injection
  • Already has all of your App Icons added so all you need to do is drop in the replacement files from File Explorer or Finder. There is also a link in there so you can see how to get all of your icons generated for you correctly in all of the sizes with all of the correct naming.
  • Starts you off with some base colors to use for your project with information of how to develop a Material Design pallet for your application.
  • By default it already has everything you need for Localizing strings in XAML
  • It's cross platform, using dotnet new you get the same experience from the command line whether on Mac or PC.
  • Item templates to generate Views and ViewModels with support for the common Xamarin Forms pages as well as PopupPages
  • Makes it easier to inject variables at Build to protect sensitive project secrets.
  • Quickstart with a fully working Todo app working with in memory data, Realm, or Azure Mobile Client
  • Included config for MFractor

*NOTE: Autofac & Ninject will be reintroduced once Prism 7 has a public preview.

Best Practices

App development can be simultaneously fun and frustrating. So many developers love Xamarin Forms because it really narrows down the number of API's you need to work with. What it doesn't do is eliminate your need to understand the platform your application will run on. These templates will not eliminate that need either, however they do set you down the right path, with some basic things like a splash screen so your user will at least see something while your app loads. Also included by default is the MVVM Helpers library from James Montemagno so that you can use his ObservableRangeCollection<T> to reduce the notifications sent to the UI when updating or replacing multiple items in your collection. If you don't use it MVVM Helpers you still get a ViewModelBase that will incorporate these properties as well as well as IDeviceService and virtual implementations of INavigationAware, IActiveAware, and IApplicationLifecycle.

Prism

Continuing really with Best Practices, these templates use Prism for Xamarin Forms. Currently the templates support DryIoc and Unity for Dependency Injection. Autofac and Ninject will be added back in once there is a publicly available release of Prism 7.

TabbedPages

Working with TabbedPages has traditionally been one of the more challenging areas of working with Prism. With the QuickStart template this challenge disappears. The template includes two base implementations for a TabbedPage, the PrismTabbedPage and the DynamicTabbedPage. If your TabbedPage inherits from PrismTabbedPage, it will automatically pick up and pass on the NavigationParameters to the Child Pages allowing you to properly initialize them. If you use the DynamicTabbedPage you only need to reference it in your Navigation URI and pass in variables like:

NavigationService.NavigateAsync("TabbedPage?tab=ViewA&tab=ViewB&tab=ViewC");

But it actually gets a little better than that because not only does it pick up tabs but you can also do some deep linking like:

NavigationService.NavigateAsync("TabbedPage?tab=NavigationPage/ViewA/ViewD&tab=NavigationPage/ViewB&tab=ViewC");

This means you can actually support scenarios where your actual tabs contain their own NavigationStack independent of the rest of the application.

App Icons

Applications need a lot of icons and really the templates out there don't do a very good job with App Icons. Most templates out there just leave your deployed app with a broken icon image and require some time getting the icons setup. These templates start you off with icons for your Android and iOS projects. But more than that is the GettingStarted document included in the template gives you the information you need to be able to quickly and efficiently generate a full icon set that you can drop in to replace the default icons with your own icons. Following along with Best Practices, you'll find that the iOS project is using the newer appiconset approach with the app icons as ImageAssets rather than having them in the Resources folder as BundleResources. Similarly on Android you'll find the app icon's are all in the mipmap folders rather than drawable.

Material Design

While my purpose is not to teach Material Design, there are some basics that we can easily include in the template to get you started down the right path. That includes a basic color pallet with information of how to choose new colors. There is also already a Style defined for you to customize the look and feel of a NavigationPage using those colors.

Localization

One of the things I hear over and over, developers in the United States forget some people don't speak English. For most US based dev's Localization is a complete and total afterthought. Interestingly nobody seems to have thought previously that maybe we should provide a template that assumes you want your application easily consumable by people in another country who speak another language. The quickstart template comes complete with all of the helper classes you need to get Localization working in the application and gets the Localization implemented with the DI container using Prism's IPlatformInitializer. There is also a XAML extension provided so all you need to do is include the namespace in your XAML file and use it as needed. The app of course also includes a single Resx file to get you started. You simply need to add the string resources you want to use in your application.

Cross Platform

It might seem weird when we're talking about Xamarin, but seriously it gets frustrating when we're working with a Cross Platform technology and then the developer experience is completely and totally different depending on which platform you are on. One of the most common issues we can see from a templating standpoint is that if I click File -> New, it shouldn't matter whether I'm on Mac or PC, I should be able to decide if I want my project to include iOS, Android, UWP. That's not to say I don't understand that some time may be needed before you can build a UWP app on Mac, but you should at least be able to have the platform as an option so you can work on the codebase from either platform.

Item Templates

Also included are some Item Templates custom built for the included project templates. There are two basic types of Item Templates, Pages and Services. Note that there is currently no way for the dotnet templating engine to pick up what your base namespace is, so you do have to specify this from the command line.

Pages

By default when you call dotnet new prismitem you will get a page. It's assumed that you're using the ViewModelBase from the included Project templates. You can add flags to specify whether you want to implement INavigatingAware, INavigatedAware, INavigationAware, IActiveAware, or IDestructible. By default it implements INavigationAware. There is also a flag to indicate if the page is a Tabbed Child which will automatically implement IActiveAware and INavigatingAware. Currently supported page types include ContentPage, MasterDetailPage, TabbedPage (which inherits from the Quickstart PrismTabbedPage), and PopupPages.

Samples

dotnet new prismitem -namespace MyAwesomeApp -n LoginPage
dotnet new prismitem -namespace MyAwesomeApp -page PopupPage -n SomePage
dotnet new prismitem -namespace MyAwesomeApp -n CustomerDetailPage -child

Services

Chances are your app is probably using some sort of service and if you like testability like I do, then you'll really appreciate that you can create a service with Mock class that will automatically be picked up by the Quickstart template simply by building with the Mock configuration. 

Samples

dotnet new prismitem -item Service -namespace MyAwesomeApp -n LoginService
dotnet new prismitem -item Service -namespace MyAwesomeApp -n LoginService -mocks false

Secrets

All apps have secrets and other variables that we just don't want checked into source control. To better assist with this, the template includes some helpers that will regenerate the Secrets.cs with sensitive variables you want in your codebase. Both the Secrets.cs and secrets.json files have also been added to the included .gitignore, so you can finally develop apps without having to tackle the issue of keeping app secrets out of SCM.

secrets.json

{
  "AuthClientId": "{Your App Client Id}",
  "AppServiceEndpoint": "https://appservicename.azurewebsites.net/"
}

Secrets.cs

namespace YourProject.Helpers
{
    internal static class Secrets
    {
        internal const string AuthClientId = "{Your App Client Id}";

        internal const string AppServiceEndpoint = "https://appservicename.azurewebsites.net/";
    }
}

PropertyChanged.Fody

Part of the MVVM pattern is working with INotifyPropertyChanged. Unfortunately the code can get a bit tedious. 

public class ViewAViewModel : BindableBase
{
    private string _title;
    public string Title
    {
        get => _title;
        set => SetProperty(ref _title, value);
    }

    private MyModel _selectedItem;
    public MyModel SelectedItem
    {
        get => _selectedItem;
        set => SetProperty(ref _selectedItem, value, onChanged: OnSelectedItemChanged);
    }

    private void OnSelectedItemChanged()
    {
        // Do Stuff
    }
}

With PropertyChanged.Fody already included our ViewModels and other Observable objects simply become:

public class ViewAViewModel : BindableBase
{
    public string Title { get; set; }

    public MyModel SelectedItem { get; set; }

    private void OnSelectedItemChanged()
    {
        // Do Stuff
    }
}

Mobile Center

Also bundled into this template is support for the Azure Mobile Center. While this is an opt in feature you can pass in your App Secret for iOS and/or Android from the command line with everything already wired up to send your analytics and crash data to the Azure Mobile Center. This includes an implementation of ILoggerFacade that will create a Mobile Center Analytics Event.

Data Providers

Apps today are so often really connected apps. The Quickstart Template provides you a fully functional TodoApp with the option to use either the Azure Mobile Apps Client with AzureMobileClient.Helpers or to use Realm. Either data provider will start you out with the ability to quickly develop your app with full online/offline sync with the bare minimum of configuration. 

Azure Mobile Client

In addition to simply using the Azure Mobile Client you can additionally decide if you want to use anonymous authentication or if you will require some sort of authentication. If you choose an authentication provider, the Quickstart will provide you base classes for everything you need to get started. This includes scaffolding for custom authentication sources and a fully working implementation for Azure Active Directory B2C with support coming for AAD, Google, Facebook and Microsoft Accounts.

Plugins

Because the full working app uses a PopupPage for the TodoItem detail page, the Quickstart includes Prism.Plugin.Popups, and also optionally includes a Barcode Scanning Service utilizing ZXing.Net.Mobile and is fully registered and configured.

Getting Started

To get started with the templates it's recommended that you install version 2.0 pre3 of the dotnet cli as this contains several fixes in the templating engine. Once that is installed you can install the templates by using the following commands in your cli.

dotnet new -i "Prism.Forms.QuickstartTemplates::*"

You should see the prismitems and prismformsempty templates. The Quickstart template is grouped with the empty template, though you may not see it listed it is still there.

# See the Help and options for the Quickstart Template
dotnet new prismforms -h

#Create your first quickstart
mkdir Contoso.AwesomeApp
cd Contoso.AwesomeApp
dotnet new prismforms -id com.contoso.awesomeapp -fr netstandard1.6 -mc -ios-secret 
     "{your ios secret}" -android-secret "{your android secret}" -data AzureMobileClient 
     -auth AADB2C -client-id "{your AADB2C application id}"
#Be sure the B2CName in secrets.json matches your AAD B2C name

 

Azure Mobile Client Helpers

To be honest, I forget now exactly when I first heard about the Azure Mobile Client library. I do however remember an initial sense of excitement for being able to add Online/Offline syncing to my apps. That excitement gradually faded a little when I started to deep dive into the library and realized that every project I wanted to use the Azure Mobile Client, meant that there were a number of helpers I would need to recreate. If you're familiar with the Azure Mobile Client, the chances are you may have seen tutorial either by or inspired by Adrian Hall's guide. Even Xamarin's "Connect App" template uses this basic approach. Honestly I don't mind providing an implementation for an interface or two in my projects, but it gets a little old when I have to redevelop everything in my projects.

It was for this reason that I decided to wrap the abstractions and some basic implementations into a reusable library. The AzureMobileClient.Helpers library wraps what you need to quickly get off the ground running with the AzureMobileClient. But it's really about more than simply providing the base classes you need to be successful. It's also about helping you to develop the code that follows best practices, and helps keep your code testable. 

So what does getting started even look like? Well let's say we have the classic TodoItem.

public class TodoItem : EntityData
{
    public string Name { get; set; }
    public string Notes { get; set; }
    public bool Done { get; set; }
}

We don't need to define any of the fields specific to our Azure Mobile Services Entity as it's already defined in the EntityData base class. Since I'm all about Developer Experiences, and trying to make things to where we have to write as little code as possible to have a fantastic app, I'll use Mobile Center to quickly setup a Mobile Backend. 

Create an Easy Table

Navigate to the Tables tab and create your first table. Note that when you first go to the Tables tab you'll be asked to link the app to your Azure account. The Mobile Center will automatically go out and provision a new Mobile App Service and setup everything in a Resource Group for your app. You should be aware that you can go into the Azure Portal at any time to manage the resource. When Mobile Center sets everything up it will use a SQLite database which is great for testing, and not so great for Production. If you want to set this up to be more than a demo, before you create your first table go into the Azure Portal and configure either a SQL Server connection or Storage connection under Mobile -> Data Connections. For this example we're not going to set up any authentication, but you can do this easily from Mobile Center. The great thing about Easy Tables is that the data store allows for a dynamic schema so all we need to provide for this is a table name and click Create.

Set the table name

Really with very little effort and Zero code on your part, your mobile backend is ready. Notice I said it's 'Zero code on your part', and not 'Zero code'. Behind the scenes it is setting up a Node.js backend adding the files you need. You can go into the App Service Editor at any time and make manual changes if you need to. All you need to do now is setup your Xamarin application. Keeping things simple let's set up the application using Prism with a NetStandard1.4 Core library so that we can use the latest NetStandard release of the Azure Mobile Client and the Helpers library I mentioned before.

Now in order to keep things a little easier I want to keep a singular app context that I can use so I can easily scale from 1:N models without having to update the dependencies I'm injecting into my ViewModels. To do this I'm going to reference the Container specific implementation for the library so I can more easily set this up. For this we'll use the DryIocCloudAppContext and provide our Tables very much like we would using Entity Framework and the DbContext.

public class AwesomeAppContext : DryIocCloudAppContext
{
    public AwesomeAppContext(IContainer container)
        : base(container, AppSettings.DbName)
    {
    }

    // NOTE: This must be here for the AppContext to pick up your Model Type
    // and ensure that the table is created in the SQLite store
    ICloudSyncTable<TodoItem> TodoItems => SyncTable<TodoItem>();
}

Now, we just need to register our services:

protected override void RegisterTypes()
{
    Container.Register(typeof(ICloudSyncTable<>), typeof(AzureCloudSyncTable<>), reuse: Reuse.Singleton);
    Container.RegisterInstance<IMobileServiceClient>(new MobileServiceClient(AppSettings.BackendUri));
    Container.Register<AwesomeAppContext>(Reuse.Singleton);

    Container.RegisterTypeForNavigation<NavigationPage>();
    Container.RegisterTypeForNavigation<MainPage>();
    Container.RegisterTypeForNavigation<TodoItemDetailPage>();
}

With our services we're all set. We just need to add AwesomeAppContext to the constructor of our ViewModel and we can access our data. 

public class MainPageViewModel : BaseViewModel, INavigatedAware
{
    private AwesomeAppContext _context { get; }

    public MainPageViewModel(AwesomeAppContext context)
    {
        _context = context;
        TodoItems = new ObservableRangeCollection<TodoItem>();
    }

    public ObservableRangeCollection<TodoItem> TodoItems { get; }

    public async void OnNavigatedTo(NavigationParameters parameters)
    {
        await _context.TodoItems.SyncAsync();
        TodoItems.ReplaceRange(await _context.TodoItems.ReadAllItemsAsync());
    }
}

Finally we can go from idea to working app in under 10 minutes with full Online/Offline Sync. You can see the full working TodoDemo app on GitHub.

Xamarin Package Authoring

Whether you're just a .NET developer or a Xamarin developer we've all used NuGet. Chances are if you're anything like me, you may have started down the development path on some project and developed out some really awesome tools to help you. Then maybe you were in a fancy design meeting. Maybe you were busy thinking how Rome didn't become a great Empire by having meetings... 

Rome didn't have meetings

Perhaps you're more like me and you were either at Starbucks or on your way to Starbucks, and a great idea struck. Then you realized that all of the functionality you need you just implemented on this other project. Obviously the answer is to decouple the code you wrote from your last project and put it into it's own project. The problem you ran into though is that you develop on a Mac and NuGet is for PC right?

Now I could go into authoring packages with the new csproj format using dotnet pack. But truthfully that is a topic all by itself. It's actually something that many developers may not realize you can do. I mean if you go to NuGet.org all you can find is the download for the Windows exe. What people may not realize though is that it's much easier to start authoring packages using the Xamarin toolset than you may realize.

When you installed Xamarin Studio or the newly released Visual Studio for Mac along with the IDE and tooling for Android & iOS development, you actually got Mono. Now if you go to Google and search for Mono because you have no clue what I'm talking about, don't worry, we're not talking about the infectious disease. If you go down under WebMD to the Mono Project you'll see what we're talking about. Bundled in Mono is NuGet and even better the executable is already added to your path so once you open the terminal you can just execute NuGet commands. Now there is one caveat, and it is an important one. Mono for some unknown reason refuses to update the bundled version from 2.12 so you're good if you want to query a NuGet feed or pull a package, but that's pretty much it. Fear not though, you just need to run sudo nuget update -self, and it will update to the latest version the same as if you ran it on Windows. 

There are of course some gotcha's here:

  1. If you're building platform specific code that includes the full net framework like net45 you're going to have to build the source on Windows. That said if you built it on your PC but maybe had the project in your DropBox then you can pack the Windows built binary on the Mac
  2. Xamarin Studio/Visual Studio for Mac updates. The updates typically include an Update for Mono which will reset your NuGet version back to 2.12 unless they ever decide to update the bundled version so after running updates on the IDE you will need to update NuGet before packing your projects.

A Dot Net Developer on a Mac

Recently I had a chance to attend a meetup here in San Diego. To be honest, around other developers I sometimes feel like the odd man out. I mean here I am a C# Dot Net developer, and I'm showing up to code with a Mac. It really wasn't all that long ago that you might look at a "C# Developer" doing something like that, as if they were on crack. But the times they are changing. In fact, at that meetup the odd man out, was the dev with a Windows Laptop.

I often have conflicting feelings about my development. On the one hand, I absolutely LOVE Visual Studio. As far as I'm concerned it hands down beats every other IDE out there. As I mentioned though, when I'm on the go, more often than not I'm working off my Mac. So then how on earth does a Dot Net developer work on a Mac. Well truthfully if it wasn't for all of the hard work coming from Microsoft the past few years I'm not sure it would be anywhere near as pleasant as it is now.

I realize that there are still a lot of short comings with NetStandard, for one it is completely useless for Xamarin libraries that contain XAML files. That said the work that has been done around the NetStandard has been instrumental in making Dot Net even a citizen in non-Windows environments. Part of the problem with being a Dot Net developer outside of Windows is that the tooling was heavily integrated with Windows, so it wasn't as easy as install Mono... go...

I have been gleefully watching over the past couple of years as all of that has started to change. One of my recurring issues, and frankly one that may have caused me to pull out a lot of hair, was that Microsoft kept increasing the developer experience around PowerShell. Well that's cool, but everyone else in the world is using Bash and PowerShell wasn't available outside of Windows. So to me I kept asking how stupid can you be to increase the dependency on a Windows Environment? Well truth be told they were working on porting PowerShell and it is actually available for Mac and Linux now so any PowerShell commands I may have been running in the past on PC, are now available on Mac.

But it really doesn't end with PowerShell. For the past year I have been somewhat vocal about what they call "Visual Studio for Mac", or as I call it "Xamarin Studio with a Visual Studio logo". This week the team released Preview 6 for VS for Mac. For the first time Mac users like myself are getting a lot closer to some of the critical pieces that have been missing. Now you may have noticed that until now, I haven't mentioned Visual Studio Code. It's not a bad editor, in fact I use it when writing articles for this blog. It's a great environment as well for quickly working up an AspNetCore website and running it locally. But it's been a little frustrating as a Dot Net developer that there hasn't been any tooling (other than PowerShell) that would allow me to connect to Azure and deploy resources right from the IDE. Preview 6 really changes things though. First it brings tooling directly into the IDE to deploy an AspNetCore application straight to Azure whether to an existing resource or a new resource you want to create. The next piece of critical functionality of course... C# 7. It may have taken a month longer, but it's finally available on Mac, proof they really are using the same Rosyln as Visual Studio???

The Hamburger Menu with Prism Forms

How many times have you heard someone ask about a Hamburger menu in Xamarin Forms? It's a topic that comes up fairly frequently and it seems there are two distinct camps. Those who will tell you it's drop dead simple, and those who are stuck trying to figure out why if it's so simple, they can't figure it out. Honestly there are already a ton of YouTube videos and Blog Posts on the topic, so much so that I didn't want to touch the subject. However there is still a ton of confusion about the "Secret Sauce".

 

I would like to think the reality is somewhere in between. So often I find the major reason for these types of disagreement, has more to do with mis-managed expectations. For those stuck trying to figure out how to implement the Hamburger Menu, I think there are two key "gotcha's".

 

I've seen a number of blogs on the topic, but it seems like they're quick to say just use a MasterDetailPage. Ok you're done, you don't have to go home, but don't stay here. But that isn't the whole story. I've seen some blogs that do make more of a point to tell you that your Detail Page must be wrapped in a NavigationPage. But again, that just isn't the whole story.

 

So how on earth do you get that hamburger menu? Well for starters, you don't go to McDonalds (or for those in my neck of the woods, In N Out). When people ask about the "hamburger menu" they aren't asking how do you implement a slide out menu in your app. But that's what we keep telling people. In order to get the "hamburger menu", you need images. See people kept telling you it was easy. The secret sauce is to add an Icon to the Master page of the MasterDetailPage. Xamarin actually does this in their sample, but seems to gloss over the importance.

 

Since I'm a Prism guy though, let me go over the creation of a Prism App with a Hamburger Menu. I will assume you have the basic Prism App setup.

 

App.xaml.cs
public partial class App : PrismApplication
{
    public App( IPlatformInitializer initializer = null ) 
        : base( initializer )
    {

    }

    protected override void OnInitialized()
    {
        InitializeComponent():
        NavigationService.NavigateAsync("MainPage/NavigationPage/ViewA");
    }

    protected override void RegisterTypes()
    {
        Container.RegisterTypeForNavigation<NavigationPage>();
        Container.RegisterTypeForNavigation<MainPage>();
        Container.RegisterTypeForNavigation<ViewA>();
        // So on and so forth...
    }
}
You'll notice here that there are three View's I'm registering. The first is just simply the Xamarin Forms NavigationPage. There's no magic here. The next is my MainPage, which I will go more into detail. And lastly I register ViewA which is just some View that I will have as a Detail Page.

MainPage.xaml
<?xml version="1.0" encoding="UTF-8"?>
<MasterDetailPage
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Class="HamburgerMenu.Views.MainPage">
    <MasterDetailPage.Master>
        <!-- Hamburger Menu Secret Sauce... Add an Icon!!!! Make sure it's in your resources for your Platform Project -->
        <NavigationPage Title="Required Foo" Icon="hamburger.png">
            <x:Arguments>
                <ContentPage Title="Menu">
                    <StackLayout Padding="40">
                        <Label Text="{Binding UserName,StringFormat='Hello, {0}'}" />
                        <Button Text="View A" Command="{Binding NavigateCommand}" CommandParameter="Navigation/ViewA?message=Did%20you%20see%20the%20secret%20sauce%3F" />
                        <Button Text="View B" Command="{Binding NavigateCommand}" CommandParameter="Navigation/ViewB?message=Told%20you%20Prism%20Rocks%21%21%21" />
                        <Button Text="View C" Command="{Binding NavigateCommand}" CommandParameter="Navigation/ViewC?message=Does%20the%20hamburger%20make%20you%20hungry%3F%3F%3F" />
                    </StackLayout>
                </ContentPage>
            </x:Arguments>
        </NavigationPage>
    </MasterDetailPage.Master>
</MasterDetailPage>
All code means stuff, and there's a bit going on. Whether I'm coding or not, I'm generally a very light hearted kind of guy that likes to joke around. So you'll notice here the Navigation Page that I have as the MasterDetailPage.Master, has a title of "Required Foo". That is because Title is a required field for the Master, while the Icon is optional. The icon when supplied hides the title. I mentioned that a NavigationPage is a requirement for the "Hamburger Menu", but that is for the Detail, NOT the Master. I am choosing to use the NavigationPage in my Master in this sample, not because I expect actual navigation within the 'Menu', but rather because it quickly gives me the ability to add a nice Header and Toolbar Menu Items.

Now before you go all crazy trying to figure it out. You can download this zip for the Hamburger Icon assets for Android and iOS.