Xamarin.UWP DryIoC error: Code generation not supported on this platform

If you are getting the following error when using DryIoC with Xamarin.Forms on UWP:

System.PlatformNotSupportedException: Dynamic code generation is not
supported on this platform.
at System.Reflection.Emit. TypeBuilder.GetMethod (Type, Methodinfo) + 0x2d
at
Dryloc.FastExpressionCompiler.LightExpression.ExpressionCompiler.CompileNoA
rgsNew(Constructorlnfo, Type, Type[, Type) + 0x5b
at
Dryloc.FastExpressionCompiler.LightExpression.ExpressionCompiler.TryCompileB
oundToFirstClosureParam(Type, Expression, IParameterProvider, Typel, Type.
CompilerFlags) + 0x73
at Dryloc.FactoryDelegateCompiler.CompileToFactoryDelegate(Expression.
Boolean) + 0x14c
at Dryloc.Container.Dryloc.IResolver.Resolve(Type, IfUnresolved) + 0x23c

Then instantiate your container with this code:

Container = new Container(rules =>
{
    // https://github.com/dadhi/DryIoc/blob/master/docs/DryIoc.Docs/ResolutionPipeline.md
    return rules.WithUseInterpretation();
});

The reason why you need to do this is here: DryIoc/ResolutionPipeline.md at master · dadhi/DryIoc · GitHub

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

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 6 months. 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

.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 6 months. 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.

Run .NET MAUI apps with Visual Studio for Mac

VS for Mac 17.0 Preview version is not yet supporting MAUI applications. But you can run them on macOS too, but you will need a terminal window for it!

MAUI projects can not be set as a runnable project (yet)
.NET 6 Xamarin and MAUl projects are not supported with this version of Visual Studio. The included target frameworks are not supported: net6.0-android|net6.0-ios|net6.0-maccatalyst

If you are not familiar, how to set up your environment to start developing with .NET newest technology named MAUI, then read this article by me: https://www.banditoth.hu/2021/12/29/setup-net-maui-project-on-macos/

Build and run on macOS

Open up a terminal, and navigate next to your .sln file. Give out the following command:

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

This will run your application on macOS. If you wish, you can change the last parameter to net6.0-android or net6.0-ios too.

This content has 6 months. 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.

Xamarin.Forms: Android app forgets the style when using DynamicResource

If you break the look and feel of the app when you switch apps on mobile, and you use styles as DynamicResources, which you add as MergedDictionaries in App.Xaml,
you should pay attention to this:

When you don’t exit the Android app, but bring it back to the foreground after a very long time, the constructor logic in App.xaml.cs runs again. Don’t forget to add MergedDictionary from code, which contains the styles. If you forget this, all controls will appear in the app with their default look.

I wrote about how to handle restarting the application here: https://www.banditoth.hu/2021/03/22/xamarin-forms-reopening-application-best-pratices/

This content has 6 months. 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.