AuthenticationMiddleware.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Text.Encodings.Web;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Microsoft.AspNetCore.Authentication
{
    public abstract class AuthenticationMiddleware<TOptions> where TOptions : AuthenticationOptions, new()
    {
        ...
        //snipped for clarity

        public async Task Invoke(HttpContext context)
        {
            var handler = CreateHandler();
            await handler.InitializeAsync(Options, context, Logger, UrlEncoder);
            try
            {
                if (!await handler.HandleRequestAsync())
                {
                    await _next(context);
                }
            }
            finally
            {
                try
                {
                    await handler.TeardownAsync();
                }
                catch (Exception)
                {
                    // Don't mask the original exception, if any
                }
            }
        }
        
        ...
        //snipped for clarity
    }
}