Update: Moved banditoth.hu to banditoth.net

dotnet-bot (dotnet bot) · GitHub

Some weeks ago i decided to purchase my .hu domain’s .net version. How funny is that i do love .NET stuff to develop, and the domain associated to my blog is .net? 😀 From today, you will access my blog through https://www.banditoth.net/ instead of the .hu version. No worries, you will have time to rearrange your bookmarks, because banditoth.hu is available for almost two year from now, and it redirects users to the .net version of the site.

Xamarin: Project not selected to build for this solution configuration

If your Xamarin Android, iOS or UWP application is not starting when you are hitting the Run or F5 button, then probably your Build configurations are misconfigured. This usually happens when you are opening a too old source code. No worries, we will have a solution for it.

Solution

Right click on your solution, and select configuration manager
Ensure that the desired project has the deploy column ticked.

Xamarin.UWP: Image from embedded resource throws “Operation is not supported on this platform” error

If you are getting the error “Operation is not supported on this platform” when you are trying to set an ImageResource from file for an image on Xamarin.UWP, then the problem comes from this line of code:

IconSource = ImageSource.FromResource("afolder.animage.jpg");

The solution: Image as Embadded Ressource shows “operation is not supported on this platform” in UWP and Release (microsoft.com)
In a short brief: You need to use the second parameter for FromResource method call. You must pass an assembly in order to success on UWP platform. iOS and Android is not affected with this error.

IconSource = ImageSource.FromResource("afolder.animage.jpg", typeof(AClassFromTheAssembly).Assembly);

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