BaseContentLoadedViewModel BL

BaseContentLoadedViewModel.cs

namespace <Namespace>
{
    using System;
    using System.Threading;
    using System.Threading.Tasks;
    
    public class ContentLoadedProperties : EmptyDataSetProperties
    {
        private ContentLoadedType type;

        public ContentLoadedType Type
        {
            get { return this.type; }
            set { this.SetProperty(ref this.type, value); }
        }

        public enum ContentLoadedType
        {
            Loading,
            Loaded,
            Empty,
        }
    }
    
    public interface IContentLoadedViewModel
    {
        ContentLoadedProperties ContentLoadedProperties { get; }
    }

    public abstract class BaseContentLoadedViewModel<TModel> : BaseViewModel, IContentLoadedViewModel where TModel : class
    {
        private ContentLoadedProperties contentLoadedProperties;
        private TModel model;
        private readonly CancellationTokenSource cancellationTokenSource;

        public BaseContentLoadedViewModel()
        {
            this.cancellationTokenSource = new CancellationTokenSource();
        }

        public ContentLoadedProperties ContentLoadedProperties
        {
            get => this.contentLoadedProperties ?? (this.contentLoadedProperties = new ContentLoadedProperties());
            set => this.SetProperty(ref this.contentLoadedProperties, value);
        }

        public TModel Model
        {
            get => this.model;
            set => this.SetProperty(ref this.model, value);
        }

        protected abstract string EmptyModelTitle { get; }

        protected virtual bool LoadModelOnStart => true;

        // protected virtual bool ShowLoadingWhenLoadModel => true;

        public override void Start()
        {
            base.Start();
            if (this.LoadModelOnStart)
            {
                this.LoadModelInBackground();
            }
        }

        protected abstract Task<TModel> LoadModel(CancellationToken cancellationToken);

        protected virtual async Task ReloadModel()
        {
            try
            {
                this.ContentLoadedProperties.Type = ContentLoadedProperties.ContentLoadedType.Loading;
                var newModel = await PollyWrapper.Execute(this.LoadModel, this.LoadModelFromCache, this.cancellationTokenSource.Token);
                this.SetModel(newModel);
                if (newModel == null)
                {
                    this.ContentLoadedProperties.Title = this.EmptyModelTitle;
                    this.ContentLoadedProperties.Type = ContentLoadedProperties.ContentLoadedType.Empty;
                }
                else
                {
                    this.ContentLoadedProperties.Type = ContentLoadedProperties.ContentLoadedType.Loaded;
                }
            }
            catch (Exception ex)
            {
                this.ContentLoadedProperties.Title = ex.Message;
                this.ContentLoadedProperties.Type = ContentLoadedProperties.ContentLoadedType.Empty;
            }
        }

        protected virtual TModel LoadModelFromCache(Exception ex)
        {
            return default(TModel);
        }

        protected virtual async void LoadModelInBackground()
        {
            await this.ReloadModel();
        }

        protected virtual void SetModel(TModel model)
        {
            this.Model = model;
        }
    }
}