Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Christian Liebel @christianliebel Consultant

Blazor WebAssembly Blazor Server Blazor Hybrid Calling arbitrary platform-specific interfaces ❌ (only when packaged) ✅ (server only) ✅ Support for offline capability ✅ ❌ ✅ Executable in browsers ✅ ✅ ❌ Packageable for mobile/desktop plattorms ✅ ❌ ✅ Code can be kept secret ❌ ✅ ❌ Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen One Blazor in three flavors

SPA Model Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Blazor WebAssembly

Responsive Linkable Discoverable Installable App-like Connectivity Independent Fresh Safe Re-engageable Progressive Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

https://paint.js.org – Productivity app – Draw images – Lots of actions & tools – Installable – Read/save files – Copy/paste images from/to clipboard – Share files to other apps – Register for file extensions Demo Use Case Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Web App Manifest Service Worker Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Web App Manifest Distinguishes Web Apps from Websites JSON-based file containing metadata for apps only Apps can be identified by search engines, app store providers, etc. PWA Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

manifest.webmanifest { "short_name": "Paint", "name": "Paint Workshop", "theme_color": "white", "icons": [{ "src": "icon.png", "sizes": "512x512" }], "start_url": "./", "display": "standalone", "shortcuts": [/* … */] } PWA Names Icons Display Mode Shortcuts Start URL Theme color (status bar/window bar) Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Blazor Support The Blazor PWA template adds a web app manifest and service worker support Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen PWA

Web App Manifest – Installability Criteria Web App is not already installed User clicked the page at least once and had it open for at least 30 seconds (at any time) Includes a Web App Manifest that has short_name or name, at least a 192px and 512px icon, a start_url and a display mode of fullscreen, standalone or minimal-ui Served over HTTPS Registers a service worker with a fetch event handler (will change!) https://web.dev/install-criteria/#criteria PWA Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Service Worker JavaScript snippet executed in an own thread, registered by the website Acts as a controller, proxy, or interceptor Has a cache to store responses (for offline availability and performance) Can wake up even when the website is closed and perform background tasks (e.g., push notifications or sync) PWA Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Service Worker PWA Service Worker Internet Website HTML/JS Cache fetch Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Blazor Service Worker The Blazor PWA template includes a custom service worker implementation All Blazor assets are precached by default Service Worker behavior can be modified (e.g., for push) à maximum flexibility PWA Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Push Notifications Just as native apps, PWAs can receive push notifications Combination of two technologies: Web Notifications and Push API Supported by Chrome, Edge, Firefox, Safari (on macOS) Support coming to iOS and iPadOS in version 16.4 Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen PWA

Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Project Fugu Capabilities »Let’s bring the web back – API by API« Thomas Steiner, Google Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Capabilities https://goo.gle/fugu-api-tracker Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Browser Capabilities navigator.share({ url: 'http://example.com' }); ShareIntent DataTransferManager … NSSharingServicePicker Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

…and Blazor But: Most Fugu APIs are JavaScript-based Accessing JavaScript APIs from Blazor is relatively hard Solution: Wrapper packages that make JavaScript APIs accessible in C# Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Capabilities

Open-source NuGet packages API NuGet Package Async Clipboard API Thinktecture.Blazor.AsyncClipboard Badging API Thinktecture.Blazor.Badging File System API KristofferStrube.Blazor.FileSystem File System Access API KristofferStrube.Blazor.FileSystemAccess File Handling API Thinktecture.Blazor.FileHandling Web Share API Thinktecture.Blazor.WebShare Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Capabilities

Async Clipboard API Allows reading from/writing to the clipboard in an asynchronous manner (UI won’t freeze during long-running operations) Reading from the clipboard requires user consent first (privacy!) Supported by Chromium- based browsers and Safari Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Async Clipboard API var clipboardItem = new ClipboardItem( new Dictionary { { "image/png", imagePromise } }); await _asyncClipboardService.WriteAsync( new[] { clipboardItem } ); Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Web Share API Allows sharing a title, URL, text, or files API can only be invoked as a result of a user action (i.e. a click or keypress) Supported by Chrome on Windows and Chrome OS, Edge, Safari Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Web Share API var data = new WebShareDataModel { Files = new[] { fileReference } }; await _shareService.ShareAsync(data); Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

File System Access API Some applications heavily rely on working with files (e.g. Visual Studio Code, Adobe Photoshop, …) File System Access API allows you to open, save and override files and directories Supported by Chromium- based browsers on desktop Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

File System Access API try { var fileHandles = await _fileSystemAccessService .ShowOpenFilePickerAsync (_filePickerOptions); _fileHandle = fileHandles.Single(); } catch (JSException ex) { Console.WriteLine(ex); } Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

File System Handling API Register your PWA as a handler for file extensions Requires installing the application first Declare supported extensions in Web App Manifest and add imperative code to your application logic Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

File System Handling API "file_handlers": [{ "action": "./", "accept": { "text/plain": [".txt"] } }] Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

File System Handling API await _fileHandlingService.SetConsumerAsync(async (launchParams) => { foreach (var fileSystemHandle in launchParams.Files) { if (fileSystemHandle is FileSystemFileHandle fileSystemFileHandle) { var file = await fileSystemFileHandle.GetFileAsync(); var text = await file.TextAsync(); Console.WriteLine(text); } } }); Capabilities Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Badging API Displays a badge on the installed application’s icon as a less obtrusive alternative to notification banners Well known from applications like email clients, instant messengers, or to-do apps Requires your application to be installed Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Capabilities

Badging API await badgingService.SetAppBadgeAsync(3); Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Capabilities

Overview Use available interfaces and functions of a system (opposite of Graceful Degradation) Users with modern, feature-rich browsers get a better experience Apps are available on older browsers, but with limited functionality Concept: Browser feature support should grow over time—thereby more users can enjoy an increasing number of features Progressive Enhancement Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Overview if (await _fileSystemAccessService.IsSupported()) { // use API } else { // use fallback or disable feature } Check whether an API/feature is available. If yes—use it! Otherwise: 1. Disable/hide the functionality 2. Fall back to an alternative API (if available) Progressive Enhancement Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Disabling unsupported features Copy Paste Share Progressive Enhancement Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Providing an alternative implementation await _imageService.DownloadAsync(await _canvas!.ToDataURLAsync()); Progressive Enhancement Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Deployment Electron/Capacitor JS HTML CSS .ipa .exe .app ELF .apk .appx Single-Page Application Capacitor/Cordova Electron/Tauri Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

– Productivity apps – IDEs, code editors – Video editors – Image editors – Office applications – Document editors – Presentation apps – Enterprise applications Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Use Cases

Spotify Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Use Cases https://open.spotify.com/

VS Code Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Use Cases https://vscode.dev/

Photoshop Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Use Cases https://creativecloud.adobe.com/cc/photoshop

PWA – Installation may not be obvious – Only web platform APIs can be called – Antivirus software or cloud sync agents can’t be implemented – Some APIs may not be available on all browsers and OS’s Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Limitations

Blazor – C#, but knowledge of HTML, CSS and JS will still be required – Rider support is not great – Caching can lead to confusion while testing – Very large bundles = high initial loading time (mobile users!) – Blazor WebAssembly: 2 MB (without culture info) – Angular: 50 kB – Firewalls may block the transfer of DLL files – Summary: Maybe not the best solution for B2C apps where the environment cannot be controlled Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Limitations

PWA – Write once, run anywhere becomes reality – Web apps continue to become more powerful, on all platforms Blazor – Blazor is interesting for teams with C# and .NET knowledge – Data models may be shared between client and server – Existing (legacy) code may be transferred to the web Progressive Web Apps mit Blazor Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Success Stories

Blazor: Reuse your existing C# and .NET knowledge and implement great applications that run just fine in the browser and all relevant OS’s PWA: Improve the experience by allowing users to install your app and run it offline Fugu: Add capabilities for an even deeper integration with the OS using C#-based NuGet packages Progressive Enhancement: Ensure that users of older or less powerful browsers can still use the app Let’s build great apps for the web! Summary Einsatzgebiete, Erfolgsgeschichten, Einschränkungen Progressive Web Apps mit Blazor

Thank you for your kind attention! Christian Liebel @christianliebel [email protected] https://www.thinktecture.com/ueber-uns/karriere/