The MVVM pattern separates the interface (View) from presentation logic (ViewModel). The CommunityToolkit.Mvvm package removes almost all the boilerplate thanks to source generators.

A complete ViewModel

public partial class ProfileViewModel(IProfileService service) : ObservableObject
{
    [ObservableProperty]
    [NotifyCanExecuteChangedFor(nameof(SaveCommand))]
    public partial string Name { get; set; } = "";

    [ObservableProperty]
    public partial bool IsSaving { get; set; }

    private bool CanSave() => !string.IsNullOrWhiteSpace(Name) && !IsSaving;

    [RelayCommand(CanExecute = nameof(CanSave))]
    private async Task SaveAsync()
    {
        IsSaving = true;
        try { await service.SaveAsync(Name); }
        finally { IsSaving = false; }
    }
}

The generator creates the property change notifications and the SaveCommand command, which enables and disables itself based on CanSave.

The View

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:vm="clr-namespace:MyApp.ViewModels"
             x:DataType="vm:ProfileViewModel">
    <VerticalStackLayout Padding="20" Spacing="12">
        <Entry Text="{Binding Name}" Placeholder="Name" />
        <Button Text="Save" Command="{Binding SaveCommand}" />
        <ActivityIndicator IsRunning="{Binding IsSaving}" />
    </VerticalStackLayout>
</ContentPage>

x:DataType enables compiled bindings: checked at compile time and faster at runtime.

Registration

builder.Services.AddSingleton<IProfileService, ProfileService>();
builder.Services.AddTransient<ProfileViewModel>();
builder.Services.AddTransient<ProfilePage>();

The page receives the ViewModel in its constructor and assigns it to the BindingContext. To let different ViewModels communicate without direct references, use WeakReferenceMessenger, which replaces the old MessagingCenter.