Blazor

Client:

using Blazor.Client;
using Microsoft.AspNetCore.Components.Web;
using Microsoft.AspNetCore.Components.WebAssembly.Authentication;
using Microsoft.AspNetCore.Components.WebAssembly.Hosting;

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

var services = builder.Services;

RegisterHttpClient(builder, services);

builder.Services.AddOidcAuthentication(options =>
{
    options.ProviderOptions.MetadataUrl = "http://localhost:8080/realms/Test/.well-known/openid-configuration";
    options.ProviderOptions.Authority = "http://localhost:8080/realms/Test";
    options.ProviderOptions.ClientId = "test-client";
    options.ProviderOptions.ResponseType = "id_token token";
    //options.ProviderOptions.DefaultScopes.Add("Audience");

    options.UserOptions.NameClaim = "preferred_username";
    options.UserOptions.RoleClaim = "roles";
    options.UserOptions.ScopeClaim = "scope";
});

var app = builder.Build();

await app.RunAsync();

static void RegisterHttpClient(
    WebAssemblyHostBuilder builder,
    IServiceCollection services)
{
    var httpClientName = "Default";

    services.AddHttpClient(httpClientName,
        client => client.BaseAddress = new Uri(builder.HostEnvironment.BaseAddress))
            .AddHttpMessageHandler<BaseAddressAuthorizationMessageHandler>();

    services.AddScoped(
        sp => sp.GetRequiredService<IHttpClientFactory>()
            .CreateClient(httpClientName));
}

Server:

using System.Globalization;
using Keycloak.AuthServices.Authentication;
using Microsoft.OpenApi.Models;
using Serilog;
using Serilog.Events;

var builder = WebApplication.CreateBuilder(args);
var services = builder.Services;
var configuration = builder.Configuration;

services.AddControllersWithViews();
services.AddRazorPages();

services.AddEndpointsApiExplorer();
var openIdConnectUrl = $"{configuration["Keycloak:auth-server-url"]}realms/{configuration["Keycloak:realm"]}/.well-known/openid-configuration";

services.AddSwaggerGen(c =>
{
    var securityScheme = new OpenApiSecurityScheme
    {
        Name = "Auth",
        In = ParameterLocation.Header,
        Type = SecuritySchemeType.OpenIdConnect,
        OpenIdConnectUrl = new Uri(openIdConnectUrl),
        Scheme = "bearer",
        BearerFormat = "JWT",
        Reference = new OpenApiReference
        {
            Id = "Bearer",
            Type = ReferenceType.SecurityScheme
        }
    };
    c.AddSecurityDefinition(securityScheme.Reference.Id, securityScheme);
    c.AddSecurityRequirement(new OpenApiSecurityRequirement
    {
        {securityScheme, Array.Empty<string>()}
    });
});

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Verbose()
    .WriteTo.Console(
        outputTemplate: "[{Level:u4}] | {Message:lj}{NewLine}{Exception}",
        restrictedToMinimumLevel: LogEventLevel.Information,
        formatProvider: CultureInfo.InvariantCulture)
    .CreateBootstrapLogger();

builder.Host.UseSerilog();

services.AddKeycloakWebApiAuthentication(configuration);

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseWebAssemblyDebugging();
    app.UseSwagger().UseSwaggerUI();
}
else
{
    app.UseExceptionHandler("/Error");
}

app.UseBlazorFrameworkFiles();
app.UseStaticFiles();

app.UseRouting();

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

app.MapRazorPages();
app.MapControllers();
app.MapFallbackToFile("index.html");

app.Run();

See sample source code: keycloak-authorization-services-dotnet/tree/main/samples/Blazor