mchSamples-MAUI/ch06_Others/ex_Localization3/Resources/Localization/LocalizedStringExtension.cs

using System.ComponentModel;
using System.Globalization;
using System.Reflection;

namespace ex_Localization3.Resources.Localization;

public class Localization
{
    public string Culture
    {
        get => culture;
        set
        {
            if(string.IsNullOrWhiteSpace(value)) return;
            culture = value;
            LocalizedStringExtension.Culture = culture;
        }
    }
    private string culture = "en";
}

public class LocalizedStringExtension : IMarkupExtension<string>
{
    public string Key { get; set; }
    public static string Culture
    { 
        get => culture; 
        set
        {
            if(culture == value) return;
            culture = value;
            AppRes.Culture = new CultureInfo(Culture);
            CultureChanged?.Invoke(null, EventArgs.Empty);
        } 
    } 
    private static string culture = "en";

    public static AppResourcesVM AppRes { get; set; } = new AppResourcesVM();

    public static event EventHandler? CultureChanged;

    public string ProvideValue(IServiceProvider serviceProvider)
    {
        IProvideValueTarget? provideValueTarget = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;
        CultureChanged += (src, args) => 
        {
            (provideValueTarget?.TargetObject as BindableObject)?.SetValue((provideValueTarget?.TargetProperty as BindableProperty), typeof(AppResources).GetProperty(Key, BindingFlags.NonPublic | BindingFlags.Static)?.GetValue(null) as string ?? "");
        };
        return typeof(AppResources).GetProperty(Key, BindingFlags.NonPublic | BindingFlags.Static)?.GetValue(null) as string ?? "";
    }

    object IMarkupExtension.ProvideValue(IServiceProvider serviceProvider)
    {
        return (this as IMarkupExtension<string>).ProvideValue(serviceProvider);
    }
}