Program.cs

using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Authentication.OpenIdConnect;
using Microsoft.IdentityModel.Tokens;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddControllers();

builder.Services
    .AddAuthentication(options =>
    {
        options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
        options.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
    })
    .AddCookie()
    .AddOpenIdConnect(options =>
    {
        options.Authority = builder.Configuration["IdentitySettings:Authority"];
        options.ClientId = builder.Configuration["IdentitySettings:ClientId"];
        options.ClientSecret = builder.Configuration["IdentitySettings:ClientSecret"];

        options.ResponseType = "code";
        options.SaveTokens = true;

        options.Scope.Clear();
        options.Scope.Add("openid");
        options.Scope.Add("profile");
        options.Scope.Add("email");
        options.Scope.Add("offline_access");

        options.MapInboundClaims = false;
        options.TokenValidationParameters = new TokenValidationParameters
        {
            NameClaimType = "sub",
            RoleClaimType = "role"
        };

        options.Events = new OpenIdConnectEvents
        {
            OnAuthenticationFailed = context =>
            {
                context.HandleResponse();
                context.Response.StatusCode = StatusCodes.Status500InternalServerError;
                context.Response.ContentType = "text/plain";
                return context.Response.WriteAsync(context.Exception.Message);
            }
        };
    });

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

app.UseHttpsRedirection();

app.UseRouting();

app.UseAuthentication();
app.UseAuthorization();

app.MapStaticAssets();
app.MapControllers();
app.MapRazorPages()
   .WithStaticAssets();

app.Run();