SteveSandersonMS

This document describes options and proposals for #4048.

Overall goals

Principles:

• In Razor Components, enable customers to use as much of ASP.NET Core's existing authentication/authorization/identity feature set as possible. Minimize the invention of new stuff; maximize orthogonality.
• Provide a programming model that can be consistent across Razor Components (server-side) and Blazor (client-side), so components that use authorization can still be portable across the two, even if app-level Startup.cs logic is completely different for the two runtime environments.

The Razor Components auth feature set will be mostly the same as for MVC/Pages. We'll get the same long-tail features such as integration with 3rd-party social logins, 2FA, etc. The Razor Components template will support the same four auth options during project creation, and the "Scaffold Identity" feature will be usable on existing Razor Components projects.

SteveSandersonMS

Preserving State in Server-Side Blazor applications

Server-side Blazor is a stateful application framework. Most of the time, your users will maintain an ongoing connection to the server, and their state will be held in the server's memory in what's known as a "circuit". Examples of state held for a user's circuit include:

• The UI being rendered (i.e., the hierarchy of component instances and their most recent render output)
• The values of any fields and properties in component instances
• Data held in DI service instances that are scoped to the circuit

Occasionally, users may experience a temporary network connection loss, after which Blazor will attempt to reconnect them to their original circuit so they can continue.

SteveSandersonMS

Error handling in Server-Side Blazor

Developers building Blazor applications should be aware of how the framework deals with exceptions, and what steps to take in order to maximize reliability and to detect and diagnose errors.

To recap, server-side Blazor is a stateful framework. For as long as users are interacting with your application, they maintain a connection to the server known as a circuit. The circuit holds all the active component instances, plus many other aspects of state such as the components' most recent render output and the current set of event-handling delegates that could be triggered by client-side events. If a user opens your application in multiple browser tabs, then they have multiple independent circuits.

As a high-level principle, Blazor treats most unhandled exceptions as fatal to that circuit. If a circuit is terminated due to an unhandled exception, the user can only continue by reloading the page to create a new circuit and starting again, although other circuits (e.g., th

EdCharbeneau

@if (IsLoading)
{
    @LoadingTemplate
}
else
{
    @ContentTemplate
}

@code {

EdCharbeneau

using Microsoft.AspNetCore.Components;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Reflection;
using System.Text.RegularExpressions;
public static class ExampleMetadata
{
    public static IEnumerable<MenuItem> GetItems()