Topics

C#•2y ago

✅ Best practice when using HttpClient in a class

I have a class which essentially acts as a wrapper over an HttpClient as an abstraction for a web API. This class has a field private readonly HttpClient client; which is currently set through the constructor of the class, where I'm just kind of expecting the consuming code to have configured the base address and any other configuration in regards to the client itself. However, I don't know if this is considered good practice, or if there's some other way I'm not aware of. This class should also be usable with DI, so I don't know if I instead should have an IHttpClientFactory in the constructor or something instead.

43 Replies

Thinker•2y ago

Tl;dr, I have this

public sealed class ApiWrapper
{
    private readonly HttpClient client;

    public ApiWrapper(HttpClient client) 
    {
        this.client = client;
    } 

    // ... 
}

public sealed class ApiWrapper
{
    private readonly HttpClient client;

    public ApiWrapper(HttpClient client) 
    {
        this.client = client;
    } 

    // ... 
}

Is this bad?

undisputed world champions•2y ago

as long as you don't register ApiWrapper as singleton (and recreate it somewhat regularly), i guess this is alright you can use services.AddHttpClient<ApiWrapper>(...) to configure the client and register ApiWrapper as transient i think ms calls this usage "typed client": https://learn.microsoft.com/en-us/dotnet/core/extensions/httpclient-factory#typed-clients

Thinker•2y ago

right, nice In what package exactly is AddHttpClient defined? I can't find it nvm, found it

Henkypenky•2y ago

that is IHttpClientFactory specficically TypedClient AddHttpClient<ApiWrapper>() then just DI and consume within the class

Thinker•2y ago

Actually, I don't think this will work if the wrapper is transient, because my API relies on state in the client, so I don't think recreating it for every request will work.

Henkypenky•2y ago

you can set the settings specifically for that implementation <T> it doesn't matter, ApiWrapper doesn't manage the HttpClients its just a dependency btw typedclients are transient aswell so there is nothing wrong HttpClient might get created every time, but the Handler is reused because the IHttpClientFactory persists and you get all the benefits of creation/disposal/configurations from the service provider

Thinker•2y ago

Well I don't want the HttpClient to get created every time

Henkypenky•2y ago

then don't use harold

harold

Thinker•2y ago

sure I guess

undisputed world champions•2y ago

sry i thought your ApiWrapper is a thin wrapper for the api. basically just defining convenient functions that call the httpclient-functions. have you checked out the "Basic usages" and "Named clients" in the link i posted? you can basically call _httpClientFactory.CreateClient(...); on a IHttpClientFactory to get the HttpClient, when you need it

Henkypenky•2y ago

you can probably use it inject it through DI and use the "basic usage" where you create a client and keep that client through the life of the apiwrapper life

Thinker•2y ago

eh, I'll just add the wrapper as a singleton

Henkypenky•2y ago

but you have to do it in the DI which is not that cool but i know that you know what you are doing so whatever xd

undisputed world champions•2y ago

the IHttpClientFactory will take care of caching the httpclient/handler for you and recreate them appropriately

Thinker•2y ago

I have no idea what I'm doing Smadge

Smadge

Henkypenky•2y ago

yes you do xd

Thinker•2y ago

So I should use IHttpClientFactory?

Henkypenky•2y ago

let's go again do you want a new client each time

Thinker•2y ago

So like, thing is that I'm relying on the client storing a cookie for the user being signed in, so I need that info to be retained across requests.

Henkypenky•2y ago

the factory takes care of that for you

undisputed world champions•2y ago

well if it's some kind of long running application, yes if it's just a cli command or something like that you don't have to worry about it that much

Thinker•2y ago

okay, nice It's a Blazor WASM app

Henkypenky•2y ago

make sure you do not tell the handler to disable cookies oh wait WASM runs in sandbox you can't manipulate cookies https://learn.microsoft.com/en-us/dotnet/api/system.net.http.httpclienthandler.usecookies?view=net-8.0 this doesn't work on WASM

Thinker•2y ago

So... I can't do this?

Henkypenky•2y ago

you will probably have to create a delegating handler and override sendasync then create a custom service to add/remove headers then add the DelegatingHandler to that implementation of HttpClient which is what you should be doing, the cookies of IHttpClientFactory are automatic and shared through CookieContainer which you might not want remember that blazor WASM uses Microsoft.Extensions.Http

builder.Services.AddHttpClient("NoAutomaticCookies")
    .ConfigurePrimaryHttpMessageHandler(() =>
        new HttpClientHandler
        {
            UseCookies = false
        });

builder.Services.AddHttpClient("NoAutomaticCookies")
    .ConfigurePrimaryHttpMessageHandler(() =>
        new HttpClientHandler
        {
            UseCookies = false
        });

Severity Code Description Project File Line Suppression State

Warning    CA1416    This call site is reachable on all platforms. 'HttpClientHandler.UseCookies' is unsupported on: 'browser'.    BlazorApp15

check this: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-7.0#outgoing-request-middleware that would be your DelegatingHandler which you then can add to the config of your HttpClient they are transient so don't worry about them they just do stuff in the middleware of http requests and to be fair, you should use them like 99% of the time even if you can use cookies, i wouldn't let the Factory manage them automatically recipe for disaster

Thinker•2y ago

so...

Henkypenky•2y ago

use DelegatingHandlers and typedclients

Thinker•2y ago

So I need to make a type deriving from DelegatingHandler?

Henkypenky•2y ago

just make a class that derives from it yeah and override SendAsync which is the base of all your fancy http request methods so everything will be hit also since you use TypedClients you can specify which implementation uses what DelegatingHandler and which doesn't so you can have one implementation that you do stuff in the middleware and one that does not

Thinker•2y ago

What do I need to do in SendAsync then?

Henkypenky•2y ago

whatever you want check for headers add headers log cache error handling you name it

Thinker•2y ago

yeah but what do I need to do to get cookies to work then?

Henkypenky•2y ago

if you can explain to me what you need to do maybe i can point you in the right direction

Thinker•2y ago

When I call an endpoint in my API to log the user in, the API returns a login cookie, and that cookie should be retained throughout the rest of the app.

Henkypenky•2y ago

okay what about determining what user is making the request and attach the cookie in the middleware

Thinker•2y ago

where do I get the cookie from?

Henkypenky•2y ago

database? MemoryCache? whatever works for you

Thinker•2y ago

Except the API endpoint adds the cookie to the client

Henkypenky•2y ago

wait i think i misunderstood what you want blazor does have cookies, maybe i expressed myself wrong, what doesn't work is the cookie sharing of IHttpClientFactory it's a sandbox try this https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.components.webassembly.http.webassemblyhttprequestmessageextensions.setbrowserrequestcredentials?view=aspnetcore-7.0

public class MyHttpClientHandler : HttpClientHandler {

  protected override async Task<HttpResponseMessage>         
    SendAsync(HttpRequestMessage request,
              CancellationToken cancellationToken) {
      request.SetBrowserRequestCredentials(
        BrowserRequestCredentials.Include);

    return await base.SendAsync(request, cancellationToken);
  }
}

public class MyHttpClientHandler : HttpClientHandler {

  protected override async Task<HttpResponseMessage>         
    SendAsync(HttpRequestMessage request,
              CancellationToken cancellationToken) {
      request.SetBrowserRequestCredentials(
        BrowserRequestCredentials.Include);

    return await base.SendAsync(request, cancellationToken);
  }
}

that way you get all the cookies from the client

Thinker•2y ago

How do I make the HttpClient I add through AddHttpClient use this handler? Okay nvm, changed it to a DelegatingHandler

Henkypenky•2y ago

yeah if you

builder.Services.AddHttpClient<T>()
    .AddHttpMessageHandler<YourCustomHandler>();

builder.Services.AddHttpClient<T>()
    .AddHttpMessageHandler<YourCustomHandler>();

every typed client request will go through that custom middleware

Thinker•2y ago

yeah, I figured it out The entire thing works now catok

catok

Henkypenky•2y ago

owo

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