.NET MAUI

.NET MAUI: Save any type of object in Preferences

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.NET MAUI currently have limitations of the supported types in preferences. They can only store simple data types such as strings, integers, and booleans, and do not support more complex data types such as lists or objects. This can make it difficult to store and retrieve more complex data structures.

How to store arrays and lists, or complex classes in Preferences?

The answer is currently to serialize it. Since Preferences is supporting string saving option, you can serialize your arrays and custom classes, and store the string value.

But be aware to store large amounts of data in Preferences as a string. Consider choosing SQLite to store data when there are more than 50-100 items in an array, or your class is more complex than having 25 properties. As Microsoft marks this as a limitation: Performance may be impacted if you store large amounts of text, as the API was designed to store small amounts of text.

But there are cases when it makes sense to store other types

There are cases when it is easier to store a whole complex object on disk than to store all its properties one by one by calling preferences Set. In this case you may find useful the banditoth.MAUI.PreferencesExtension.

Usage

This package is extending the basic functions of the built in MAUI Essentials IPreferences by letting the developers to save any type of object. This is done by using JSON serialization, and saving the raw jsons as strings with the default IPreferences implementation. Since JSON arrays can be serialized back to any collection type, you can use different types when Setting the value and when Getting it back.

There are several ways to access this extension.

Dependency Injection

    private readonly IPreferences preferences;

    public MainPage(IPreferences preferences)
    {
        InitializeComponent();
        this.preferences = preferences;
    }

    private void Foo()
    {
        List<string> taleItems = new List<string>()
        {
            "The quick brown fox",
            "Jumps over the lazy dog"
        };

        preferences.SetObject<List<string>>("Tale", taleItems);

        string[] taleItemsFromPreferences = preferences.GetObject<string[]>("Tale", null);
    }

Access through Preferences

If you are used to access the preferences trough the static class, you can use this tool by accessing the Default property on the Preferences class. You can call the SetObject or GetObject extension method on it.

            // Setting the value
            Preferences.Default.SetObject<IDeviceInfo>("Device_Information", DeviceInfo.Current);
            // Getting the value
            Preferences.Default.GetObject<IDeviceInfo>("Device_Information", null);

Package’s own static reference

You can also access the SetObject or GetObject method on PreferencesExtension static class.

            // Setting the value
            PreferencesExtension.SetObject<DisplayOrientation>("Last_Display_Orientation", orientation);
            // Getting the value
            PreferencesExtension.GetObject<DisplayOrientation>("Last_Display_Orientation", DisplayOrientation.Landscape);

Configure CI pipeline with .NET MAUI Release candidate (for NuGets)

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In order to do automated builds in Azure DevOps with the .NET MAUI Release Candidate release, we need a few extra steps in the pipeline configuration. I used these steps to ensure that the NuGet packages I develop are automatically compiled and uploaded to NuGet.org. In this article I won’t go into detail about how to create a CI pipeline, I just want to show you the difference from a normal CI pipeline. I haven’t tried building and deploying applications in the cloud at the moment, but it can probably be done. Also, I don’t go into how to make the package automatically go to NuGet.org, for that I recommend an earlier article (and also how to create a CI/CD pipeline): https://www.banditoth.net/2021/11/09/azure-devops-setup-private-nuget-feed-with-ci/

Since a final version of .NET MAUI has not been released as of today, in order to build our applications in the cloud, we need to install the MAUI Workload on the Agent.
If we do not do this, we may encounter the following error:

Error NETSDK1147: To build this project, the following workloads must be installed: maui-windows

Adjust your pipeline

In order to install the workload on our build agent, create a new task at the very beginning in the pipeline file, which is executes a command in the command line:

This will result the following task in the yaml file:

- task: CmdLine@2
  inputs:
    script: 'dotnet workload install maui'

The installation of the workload will take about 5 minutes.

From now on, you will be able to use .NET Maui references on the pipelines too. This will let you build your packages in the cloud.
Once MAUI will be officially available, probably you don’t need these steps.

This content has 1 year. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

The easiest and best MVVM toolkit also for .NET MAUI.

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Guys, this is unbelievable. Microsoft Community toolkit has added a tool that means you never have to worry about which MVVM framework you’re voting for. None can be as good as this one. It can be used not only for .NET MAUI, but also for other technologies (e.g. WPF). But before I sing your praises, let’s look at what this package has to offer us:

Introducing CommunityToolkit.Mvvm

First of all, you don’t need to implement INotifyPropertyChanged in ViewModels. And by that I mean not even its parent classes. Since this component is a code generator, it’s enough to make your classes partial, and the INotifyPropertyChanged implementation is done by it, instead of you. This means that your class will be supplemented with the best implementation so that you can easily use common methods like SetProperty in the setter branch of your properties. Okay, okay, but almost any MVVM framework could do this, and you didn’t even need to use a code generator, just simply derive from a parent class. I’ll do you one better: what if you didn’t have to write the setter and getter branches of the properties at all? What if the toolkit made them itself? If you could implement a property declaration from two lines of code?
Well, that’s what makes this toolkit good: It does all that for you.

And if that’s not enough, you don’t even have to bother creating Commands. The toolkit automatically creates a command for you from your methods.
But let’s see how you can use it.

Use CommunityToolkit.MVVM in .NET MAUI

Let’s see what my ViewModel looked like before I used this toolkit:

namespace Carloo.ViewModels.SignInPage
{
    public partial class SignInPageViewModel : BaseViewModel
    {
        private Command signInCommand;
        public Command SignInCommand
        {
            get { return signInCommand ?? (signInCommand = new Command(() => _ = SignIn(), () => true)); }
        }

        private string userName;
        public string UserName
        {
            get { return userName; }
            set { SetProperty(ref userName, value, nameof(UserName)); }
        }

        private string password;
        public string Password
        {
            get { return password; }
            set { SetProperty(ref password, value, nameof(Password)); }
        }

        public SignInPageViewModel()
        {

        }

        private void SignIn()
        {
            try
            {
                ...
            }
            catch (Exception ex)
            {
                // todo error
            }
        }
    }
}

And now let’s see what this Toolkit can do with source code to make life easier:

namespace Carloo.ViewModels.SignInPage
{
    [INotifyPropertyChanged]
    public partial class SignInPageViewModel
    {
        [ObservableProperty]
        private string userName;

        [ObservableProperty]
        private string password;

        public SignInPageViewModel()
        {

        }

        [ICommand]
        private void SignIn()
        {
            try
            {
                ...
            }
            catch (Exception ex)
            {
                // todo error
            }
        }
    }
}

In other ways, however, Resharper also had the tools to provide similar simplicity for implementing MVVM. But if I remember correctly, it didn’t have all that. Like, say, that you could release PropertyChanged on a completely unrelated property, even with an attribute declaration, without writing code.

        [ObservableProperty]
        [AlsoNotifyFor(nameof(CanSignIn))]
        private string _userName;

        [ObservableProperty]
        [AlsoNotifyFor(nameof(CanSignIn))]
        private string _password;


        public bool CanSignIn { get => !string.IsNullOrWhiteSpace(UserName) && !string.IsNullOrWhiteSpace(Password); }

Learn more

I am very excited about using this tool in production environments. If you want to learn more about it, please visit the following pages:
https://devblogs.microsoft.com/ifdef-windows/announcing-net-community-toolkit-v8-0-0-preview-1/
https://docs.microsoft.com/en-gb/windows/communitytoolkit/mvvm/introduction

This content has 1 year. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

.NET MAUI: App.xaml, MainPage.xaml is missing from the project

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.NET MAUI is still in beta so there are no final project templates to create a new MAUI application. The current project template omits the App.xaml, and MainPage.xaml files from the project (at least on mac), so we have to add them ourselves.

Enable on Visual Studio, to show all files

Enable showing all files

And select the missing files, then right click on them, and add them to the project.

Include the missing files to the project
This content has 1 year. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

Setup .NET MAUI project on macOS

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You may also be interested to know how Xamarin.Forms has grown and who will be its successor. I was interested too, so I took the time between the two holidays to test the .NET MAUI developed by Microsoft, so you’ll get a couple of articles about it. First, I’ll show you the installation and how I managed it under macOS.

It’s possible that by the time you read this post, you’ll be able to create a MAUI project from UI, but it’s not currently an available feature for me. However, a lot of the tutorials were outdated because .NET 6 with VisualStudio2022 has been released, and xCode 13 is not in beta either, so you can skip some unnecessary installations.

But what is definitely needed

  • macOS capable device,
  • Visual Studio 2022,
  • xCode 13.

Get started on macOS

First thing first, fire up your macOS terminal, because we will start working in that.

If you havent installed Redth’s MAUI check tool yet, lets do this with the command

dotnet tool install -g redth.net.maui.check

Once it has been successfully installed, you will see the following output

You can invoke the tool using the following command: maui-check
Tool 'redth.net.maui.check' (version '0.10.0') was successfully installed.

So it says, that you can invoke the maui-check command from now on, but it’s a lie, since some things of ZSH terminal, we need to manually fresh up the terminals internal things, otherwise the maui-check command will fail with “Unknown command”.

export PATH=$HOME/.dotnet/tools:$PATH

From now on, you can freely invoke the

maui-check

Which results you the following output:

      _   _   _____   _____     __  __      _      _   _   ___                  
     | \ | | | ____| |_   _|   |  \/  |    / \    | | | | |_ _|                 
     |  \| | |  _|     | |     | |\/| |   / _ \   | | | |  | |                  
  _  | |\  | | |___    | |     | |  | |  / ___ \  | |_| |  | |                  
 (_) |_| \_| |_____|   |_|     |_|  |_| /_/   \_\  \___/  |___|                 
                                                                                
? .NET MAUI Check v0.10.0.0 ?
────────────────────────────────────────────────────────────────────────────────
This tool will attempt to evaluate your .NET MAUI development environment.
If problems are detected, this tool may offer the option to try and fix them for
you, or suggest a way to fix them yourself.

Thanks for choosing .NET MAUI!
────────────────────────────────────────────────────────────────────────────────
⏳ Synchronizing configuration... ok
⏳ Scheduling appointments... ok

It can fix a lot of things for you automatically, watch the output carefully, it prompts that you want to fix the issues or not.

To be honest, i don’t know this command will do the work any of the things above, but if you run this, after doing the things above, its also fine:

sudo dotnet workload install maui

Create a new MAUI project

Lets find a suitable place for our new project, then give out the following command:

dotnet new maui -n YourMauiProjectName

From now on, you can leave the terminal, and start editing the project in your favourite IDE, example the VS2022

Run your very first application

Since the projects are cannot be set as run projects in Visual Studio 2022 yet, we need to run our apps from the command line with this command

dotnet build YourMauiProjectName -t:Run -f net6.0-maccatalyst

This will run your app with mac Catalyst compilation, but you can create Android and iOS versions also with this command

This content has 1 year. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.