Scott Hanselman

Using Flurl to easily build URLs and make testable HttpClient calls in .NET

June 23, '18 Comments [9] Posted in ASP.NET | DotNetCore | Open Source
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FlurlI posted about using Refit along with ASP.NET Core 2.1's HttpClientFactory earlier this week. Several times when exploring this space (both on Twitter, googling around, and in my own blog comments) I come upon Flurl as in, "Fluent URL."

Not only is that a killer name for an open source project, Flurl is very active, very complete, and very interesting. By the way, take a look at the https://flurl.io/ site for a great example of a good home page for a well-run open source library. Clear, crisp, unambiguous, with links on how to Get It, Learn It, and Contribute. Not to mention extensive docs. Kudos!

Flurl is a modern, fluent, asynchronous, testable, portable, buzzword-laden URL builder and HTTP client library for .NET.

You had me at buzzword-laden! Flurl embraces the .NET Standard and works on .NET Framework, .NET Core, Xamarin, and UWP - so, everywhere.

To use just the Url Builder by installing Flurl. For the kitchen sink (recommended) you'll install Flurl.Http. In fact, Todd Menier was kind enough to share what a Flurl implementation of my SimpleCastClient would look like! Just to refresh you, my podcast site uses the SimpleCast podcast hosting API as its back-end.

My super basic typed implementation that "has a" HttpClient looks like this. To be clear this sample is WITHOUT FLURL.

public class SimpleCastClient
{
private HttpClient _client;
private ILogger<SimpleCastClient> _logger;
private readonly string _apiKey;

public SimpleCastClient(HttpClient client, ILogger<SimpleCastClient> logger, IConfiguration config)
{
_client = client;
_client.BaseAddress = new Uri($"https://api.simplecast.com"); //Could also be set in Startup.cs
_logger = logger;
_apiKey = config["SimpleCastAPIKey"];
}

public async Task<List<Show>> GetShows()
{
try
{
var episodesUrl = new Uri($"/v1/podcasts/shownum/episodes.json?api_key={_apiKey}", UriKind.Relative);
_logger.LogWarning($"HttpClient: Loading {episodesUrl}");
var res = await _client.GetAsync(episodesUrl);
res.EnsureSuccessStatusCode();
return await res.Content.ReadAsAsync<List<Show>>();
}
catch (HttpRequestException ex)
{
_logger.LogError($"An error occurred connecting to SimpleCast API {ex.ToString()}");
throw;
}
}
}

Let's explore Tim's expression of the same client using the Flurl library!

Not we set up a client in Startup.cs, use the same configuration, and also put in some nice aspect-oriented events for logging the befores and afters. This is VERY nice and you'll note it pulls my cluttered logging code right out of the client!

// Do this in Startup. All calls to SimpleCast will use the same HttpClient instance.
FlurlHttp.ConfigureClient(Configuration["SimpleCastServiceUri"], cli => cli
.Configure(settings =>
{
// keeps logging & error handling out of SimpleCastClient
settings.BeforeCall = call => logger.LogWarning($"Calling {call.Request.RequestUri}");
settings.OnError = call => logger.LogError($"Call to SimpleCast failed: {call.Exception}");
})
// adds default headers to send with every call
.WithHeaders(new
{
Accept = "application/json",
User_Agent = "MyCustomUserAgent" // Flurl will convert that underscore to a hyphen
}));

Again, this set up code lives in Startup.cs and is a one-time thing. The Headers, User Agent all are dealt with once there and in a one-line chained "fluent" manner.

Here's the new SimpleCastClient with Flurl.

using Flurl;
using Flurl.Http;

public class SimpleCastClient
{
// look ma, no client!
private readonly string _baseUrl;
private readonly string _apiKey;

public SimpleCastClient(IConfiguration config)
{
_baseUrl = config["SimpleCastServiceUri"];
_apiKey = config["SimpleCastAPIKey"];
}

public Task<List<Show>> GetShows()
{
return _baseUrl
.AppendPathSegment("v1/podcasts/shownum/episodes.json")
.SetQueryParam("api_key", _apiKey)
.GetJsonAsync<List<Show>>();
}
}

See in GetShows() how we're also using the Url Builder fluent extensions in the Flurl library. See that _baseUrl is actually a string? We all know that we're supposed to use System.Uri but it's such a hassle. Flurl adds extension methods to strings so that you can seamlessly transition from the strings (that we all use) representations of Urls/Uris and build up a Query String, and in this case, a GET that returns JSON.

Very clean!

Flurl also prides itself on making HttpClient testing easier as well. Here's a more sophisticated example of a library from their site:

// Flurl will use 1 HttpClient instance per host
var person = await "https://api.com"
.AppendPathSegment("person")
.SetQueryParams(new { a = 1, b = 2 })
.WithOAuthBearerToken("my_oauth_token")
.PostJsonAsync(new
{
first_name = "Claire",
last_name = "Underwood"
})
.ReceiveJson<Person>();

This example is doing a post with an anonymous object that will automatically turn into JSON when it hits the wire. It also receives JSON as the response. Even the query params are created with a C# POCO (Plain Old CLR Object) and turned into name=value strings automatically.

Here's a test Flurl-style!

// fake & record all http calls in the test subject
using (var httpTest = new HttpTest()) {
// arrange
httpTest.RespondWith(200, "OK");
// act
await sut.CreatePersonAsync();
// assert
httpTest.ShouldHaveCalled("https://api.com/*")
.WithVerb(HttpMethod.Post)
.WithContentType("application/json");
}

Flurl.Http includes a set of features to easily fake and record HTTP activity. You can make a whole series of assertions about your APIs:

httpTest.ShouldHaveCalled("http://some-api.com/*")
.WithVerb(HttpMethd.Post)
.WithContentType("application/json")
.WithRequestBody("{\"a\":*,\"b\":*}") // supports wildcards
.Times(1)

All in all, it's an impressive set of tools that I hope you explore and consider for your toolbox! There's a ton of great open source like this with .NET Core and I'm thrilled to do a small part to spread the word. You should to!


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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Using ASP.NET Core 2.1's HttpClientFactory with Refit's REST library

June 20, '18 Comments [11] Posted in ASP.NET | ASP.NET Web API | DotNetCore | Open Source
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Strong by Lucyb_22 used under Creative Commons from FlickrWhen I moved my podcast site over to ASP.NET Core 2.1 I also started using HttpClientFactory and wrote up my experience. It's a nice clean way to centralize both settings and policy for your HttpClients, especially if you're using a lot of them to talk to a lot of small services.

Last year I explored Refit, an automatic type-safe REST library for .NET Standard. It makes it super easy to just declare the shape of a client and its associated REST API with a C# interface:

public interface IGitHubApi
{
[Get("/users/{user}")]
Task<User> GetUser(string user);
}

and then ask for an HttpClient that speaks that API's shape, then call it. Fabulous.

var gitHubApi = RestService.For<IGitHubApi>("https://api.github.com");

var octocat = await gitHubApi.GetUser("octocat");

But! What does Refit look like and how does it work in an HttpClientFactory-enabled world? Refit has recently been updated with first class support for ASP.NET Core 2.1's HttpClientFactory with the Refit.HttpClientFactory package.

Since you'll want to centralize all your HttpClient configuration in your ConfigureServices method in Startup, Refit adds a nice extension method hanging off of Services.

You add a RefitClient of a type, then add whatever other IHttpClientBuilder methods you want afterwards:

services.AddRefitClient<IWebApi>()
.ConfigureHttpClient(c => c.BaseAddress = new Uri("https://api.example.com"));
// Add additional IHttpClientBuilder chained methods as required here:
// .AddHttpMessageHandler<MyHandler>()
// .SetHandlerLifetime(TimeSpan.FromMinutes(2));

Of course, then you can just have your HttpClient automatically created and passed into the constructor. You'll see in this sample from their GitHub that you get an IWebAPI (that is, whatever type you want, like my IGitHubApi) and just go to town with a strongly typed interfaces of an HttpClient with autocomplete.

public class HomeController : Controller
{
public HomeController(IWebApi webApi)
{
_webApi = webApi;
}

private readonly IWebApi _webApi;

public async Task<IActionResult> Index(CancellationToken cancellationToken)
{
var thing = await _webApi.GetSomethingWeNeed(cancellationToken);

return View(thing);
}
}

Refit is easy to use, and even better with ASP.NET Core 2.1. Go get Refit and try it today!

* Strong image by Lucyb_22 used under Creative Commons from Flickr


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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Penny Pinching in the Cloud: Deploying Containers cheaply to Azure

June 15, '18 Comments [8] Posted in Azure
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imageI saw a tweet from a person on Twitter who wanted to know the easiest and cheapest way to get an Web Application that's in a Docker Container up to Azure. There's a few ways and it depends on your use case.

Some apps aren't web apps at all, of course, and just start up in a stateless container, do some work, then exit. For a container like that, you'll want to use Azure Container Instances. I did a show and demo on this for Azure Friday.

Azure Container Instances

Using the latest Azure CLI  (command line interface - it works on any platform), I just do these commands to start up a container quickly. Billing is per-second. Shut it down and you stop paying. Get in, get out.

Tip: If you don't want to install anything, just go to https://shell.azure.com to get a bash shell and you can do these command there, even on a Chromebook.

I'll make a "resource group" (just a label to hold stuff, so I can delete it en masse later). Then "az container create" with the image. Note that that's a public image from Docker Hub, but I can also use a private Container Registry or a private one in Azure. More on that in a second.

Anyway, make a group (or use an existing one), create a container, and then either hit the IP I get back or I can query for (or guess) the full name. It's usually dns=name-label.location.azurecontainer.io.

> az group create --name someContainers --location westus
Location Name
---------- --------------
westus someContainers
> az container create --resource-group someContainers --name fancypantscontainer --image microsoft/aci-helloworl
d --dns-name-label fancy-container-demo --ports 80
Name ResourceGroup ProvisioningState Image IP:ports CPU/Memory OsType Location
------------------- --------------- ------------------- ------------------------ ---------------- --------------- -------- ----------
fancypantscontainer someContainers Pending microsoft/aci-helloworld 40.112.167.31:80 1.0 core/1.5 gb Linux westus
> az container show --resource-group someContainers --name fancypantscontainer --query "{FQDN:ipAddress.fqdn,ProvisioningState:provisioningState}" --out table
FQDN ProvisioningState
--------------------------------------------- -------------------
fancy-container-demo.westus.azurecontainer.io Succeeded

Boom, container in the cloud, visible externally (if I want) and per-second billing. Since I made and named a resource group, I can delete everything in that group (and stop billing) easily:

> az group delete -g someContainers 

This is cool because I can basically run Linux or Windows Containers in a "serverless" way. Meaning I don't have to think about VMs and I can get automatic, elastic scale if I like.

Azure Web Apps for Containers

ACI is great for lots of containers quickly, for bringing containers up and down, but I like my long-running web apps in Azure Web Apps for Containers. I run 19 Azure Web Apps today via things like Git/GitHub Deploy, publish from VS, or CI/CD from VSTS.

Azure Web Apps for Containers is the same idea, except I'm deploying containers directly. I can do a Single Container easily or use Docker Compose for multiple.

I wanted to show how easy it was to set this up so I did a video (cold, one take, no rehearsal, real accounts, real app) and put it on YouTube. It explains "How to Deploy Containers cheaply to Azure" in 21 minutes. It could have been shorter, but I also wanted to show how you can deploy from both Docker Hub (public) or from your own private Azure Container Registry.

I did all the work from the command line using Docker commands where I just pushed to my internal registry!

> docker login hanselregistry.azurecr.io
> docker build -t hanselregistry.azurecr.io/podcast .
> docker push hanselregistry.azurecr.io/podcast

Took minutes to get my podcast site running on Azure in Web Apps for Containers. And again - this is the penny pinching part - keep control of the App Service Plan (the VM underneath the App Service) and use the smallest one you can and pack the containers in tight.

Watch the video, and note when I get to the part where I add create an "App Service Plan." Again, that's the VM under a Web App/App Service. I have 19 smallish websites inside a Small (sometime a Medium, I can scale it whenever) App Service. You should be able to fit 3-4 decent sites in small ones depending on memory and CPU characteristics of the site.

Click Pricing Plan and you'll get here:

Recommend Pricing tiers have many choices

Be sure to explore the Dev/Test tab on the left as well. When you're making a non-container-based App Service you'll see F1 and D1 for Free and Shared. Both are fine for small websites, demos, hosting your github projects, etc.

Free, Shared, or Basic Infrastructure

If you back up and select Docker as the "OS"...

Windows, Linux, or Docker

Again check out Dev/Test for less demanding workloads and note B1 - Basic.

B1 is $32.74

The first B1 is free for 30 days! Good to kick the tires. Then as of the timing of this post it's US$32.74 (Check pricing for different regions and currencies) but has nearly 2 gigs of RAM. I can run several containers in there.

Just watch your memory and CPU and pack them in. Again, more money means better perf, but the original ask here was how to save money.

Low CPU and 40% memory

To sum up, ACI is great for per-second billing and spinning up n containers programmatically and getting out fast) and App Service for Containers is an easy way to deploy your Dockerized apps. Hope this helps.


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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EarTrumpet 2.0 makes Windows 10's audio subsystem even better...and it's free!

June 13, '18 Comments [9] Posted in Open Source | Win10
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EarTrumpetLast week I blogged about some new audio features in Windows 10 that make switching your inputs and outputs easier, but even better, allow you to set up specific devices for specific programs. That means I can have one mic and headphones for Audition, while another for browsing, and yet another set for Skype.

However, while doing my research and talking about this on Twitter, lots of people started recommending I check out "EarTrumpet" - it's an applet that lets you control the volume of classic and modern Windows Apps in one nice UI! Switching, volume, and more. Consider EarTrumpet a prosumer replacement for the little Volume icon down by the clock in Windows 10. You'll hide the default one and drag EarTrumpet over in its place and use it instead!

EarTrumpet

EarTrumpet is available for free in the Windows Store and works on all versions of Windows 10, even S! I have no affiliation with the team that built it and it's a free app, so you have literally nothing to lose by trying it out!

EarTrumpet is also open source and on GitHub. The team that built it is:

  • Rafael Rivera - a software forward/reverse engineer
  • David Golden - lead engineer on MetroTwit, the greatest WPF Twitter Client the world has never known.
  • Dave Amenta - ex-Microsoft, worked on shell and Start menu for Windows 8 and 10

It was originally built as a replacement for the Volume Control in Windows back in 2015, but EarTrumpet 2.0's recent release makes it easy to use the new audio capabilities in the Windows 10's April 2018 Update.

Looks Good

It's easy to make a crappy Windows App. Heck, it's easy to make a crappy app. But EarTrumpet is NOT just an "applet" or an app. It's a perfect example of how a Windows 10 app - not made by Microsoft - can work and look seamlessly with the operating system. You'll think it's native - and it adds functionality that probably should be built in to Windows!

It's got light/dark theme support (no one bothers to even test this, but EarTrumpet does) and a nice acrylic blur. It looks like it's built-in/in-box. There's a sample app so you can make your apps look this sharp up on Rafael's GitHub and here's the actual BlurWindowExtensions that EarTrumpet uses.

Works Good

Quickly switch outputEarTrumpet 1.x works on Windows "RS3 and below" so that's 10.0.16299 and down. But 2.0 works on the latest Windows and is also written entirely in C#. Any remaining C++ code has been removed with no missing functionality.

EarTrumpet may SEEM like a simple app but there's a lot going on to be this polished AND work with any combination of audio hardware. As a podcaster and remote workers I have a LOT of audio devices but I now have one-click control over it all.

Given how fast Windows 10 has been moving with Insiders Builds and all, it seems like there's a bunch of APIs with new functionality that lacks docs. The EarTrumpet team has reverse engineered the parts the needed.

Modern Resource Technology (MRT) Resource Manager

Internal Audio Interface: IAudioPolicyConfigFactory

  • Gets them access to new APIs (GetPersistedDefaultAudioEndpoint / SetPersistedDefaultAudioEndpoint) in RS4 that let's them 'redirect' apps to different playback devices. Same API used in modern sound settings.
      • Code here with no public API yet?

    Internal Audio Interface: IPolicyConfig

    • Gets them access to SetDefaultEndpoint API; lets us change the default playback device
    • Code here and no public API yet?

    Acrylic Blur (win32)

    From a development/devops perspective, I am told EarTrumpet's team is able to push a beta flight through the Windows 10 Store in just over 30 minutes. No waiting for days to get beta test data. They use Bugsnag for their generous OSS license to catch crashes and telemetry. So far they're getting >3000 new users a month as the word gets out with nearly 100k users so far! Hopefully +1 as you give EarTrumpet a try yourself!


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    About Scott

    Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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    ASP.NET Core Architect David Fowler's hidden gems in 2.1

    June 11, '18 Comments [10] Posted in ASP.NET | DotNetCore
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    ASP.NET Architect David FowlerOpen source ASP.NET Core 2.1 is out, and Architect David Fowler took to twitter to share some hidden gems that not everyone knows about. Sure, it's faster, builds faster, runs faster, but there's a number of details and fun advanced techniques that are worth a closer look at.

    .NET Generic Host

    ASP.NET Core introduced a new hosting model. .NET apps configure and launch a host.

    The host is responsible for app startup and lifetime management. The goal of the Generic Host is to decouple the HTTP pipeline from the Web Host API to enable a wider array of host scenarios. Messaging, background tasks, and other non-HTTP workloads based on the Generic Host benefit from cross-cutting capabilities, such as configuration, dependency injection (DI), and logging.

    This means that there's not just a WebHost anymore, there's a Generic Host for non-web-hosting scenarios. You get the same feeling as with ASP.NET Core and all the cool features like DI, logging, and config. The sample code for a Generic Host is up on GitHub.

    IHostedService

    A way to run long running background operations in both the generic host and in your web hosted applications. ASP.NET Core 2.1 added support for a BackgroundService base class that makes it trivial to write a long running async loop. The sample code for a Hosted Service is also up on GitHub.

    Check out a simple Timed Background Task:

    public Task StartAsync(CancellationToken cancellationToken)
    {
    _logger.LogInformation("Timed Background Service is starting.");

    _timer = new Timer(DoWork, null, TimeSpan.Zero,
    TimeSpan.FromSeconds(5));

    return Task.CompletedTask;
    }

    Fun!

    Windows Services on .NET Core

    You can now host ASP.NET Core inside a Windows Service! Lots of people have been asking for this. Again, no need for IIS, and you can host whatever makes you happy. Check out Microsoft.AspNetCore.Hosting.WindowsServices on NuGet and extensive docs on how to host your own ASP.NET Core app without IIS on Windows as a Windows Service.

    public static void Main(string[] args)
    {
    var pathToExe = Process.GetCurrentProcess().MainModule.FileName;
    var pathToContentRoot = Path.GetDirectoryName(pathToExe);

    var host = WebHost.CreateDefaultBuilder(args)
    .UseContentRoot(pathToContentRoot)
    .UseStartup<Startup>()
    .Build();

    host.RunAsService();
    }

    IHostingStartup - Configure IWebHostBuilder with an Assembly Attribute

    Simple and clean with source on GitHub as always.

    [assembly: HostingStartup(typeof(SampleStartups.StartupInjection))]
    

    Shared Source Packages

    This is an interesting one you should definitely take a moment and pay attention to. It's possible to build packages that are used as helpers to share source code. We internally call these "shared source packages." These are used all over ASP.NET Core for things that should be shared BUT shouldn't be public APIs. These get used but won't end up as actual dependencies of your resulting package.

    They are consumed like this in a CSPROJ. Notice the PrivateAssets attribute.

    <PackageReference Include="Microsoft.Extensions.ClosedGenericMatcher.Sources" PrivateAssets="All" Version="" />
    <PackageReference Include="Microsoft.Extensions.ObjectMethodExecutor.Sources" PrivateAssets="All" Version="" />

    ObjectMethodExecutor

    If you ever need to invoke a method on a type via reflection and that method could be async, we have a helper that we use everywhere in the ASP.NET Core code base that is highly optimized and flexible called the ObjectMethodExecutor.

    The team uses this code in MVC to invoke your controller methods. They use this code in SignalR to invoke your hub methods. It handles async and sync methods. It also handles custom awaitables and F# async workflows

    SuppressStatusMessages

    A small and commonly requested one. If you hate the output that dotnet run gives when you host a web application (printing out the binding information) you can use the new SuppressStatusMessages extension method.

    WebHost.CreateDefaultBuilder(args)
    .SuppressStatusMessages(true)
    .UseStartup<Startup>();

    AddOptions

    They made it easier in 2.1 to configure options that require services. Previously, you would have had to create a type that derived from IConfigureOptions<TOptions>, now you can do it all in ConfigureServices via AddOptions<TOptions>

    public void ConfigureServicdes(IServiceCollection services)
    {
    services.AddOptions<MyOptions>()
    .Configure<IHostingEnvironment>((o,env) =>
    {
    o.Path = env.WebRootPath;
    });
    }

    IHttpContext via AddHttpContextAccessor

    You likely shouldn't be digging around for IHttpContext, but lots of folks ask how to get to it and some feel it should be automatic. It's not registered by default since having it has a performance cost. However, in ASP.NET Core 2.1 a PR was put in for an extension method that makes it easy IF you want it.

    services.AddHttpContextAccessor();
    

    So ASP.NET Core 2.1 is out and ready to go

    New features in this release include:

    Check out What's New in ASP.NET Core 2.1 in the ASP.NET Core docs to learn more about these features. For a complete list of all the changes in this release, see the release notes.

    Go give it a try. Follow this QuickStart and you can have a basic Web App up in 10 minutes.


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    About Scott

    Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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    Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.