How to use message handlers in .NET 6?-CodePudding

I need to add a custom header to each http request. To do so, I want to use a message handler and override SendAsync() method like so:

    public class RequestHandler : DelegatingHandler
    {
        private readonly ICorrelationIdAccessor _correlationIdAccessor;

        public RequestHandler(ICorrelationIdAccessor correlationIdAccessor)
        {
            _correlationIdAccessor = correlationIdAccessor;
        }

        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            request.Headers.Add("CorrelationId", _correlationIdAccessor.GetCorrelationId());

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

How can I register this new message handler in Program.cs using .NET 6 ?

What I did for now, is to create a HttpConfiruration object and add the RequestHandler to the MessageHandlers collection, but I don't know how to register it to the builder:

var httpConfig = new HttpConfiguration();
httpConfig.MessageHandlers.Add(new RequestHandler());

Any suggestions on how to do this, or any other ways on how to add a custom header to all the HTTP requests are welcomed.

Thank you !

CodePudding user response：

AFAIK you can do it for named/typed HttpClient created by IHttpClientFactory (see one, two):

builder.Services.AddHttpClient<SomeServiceUsingHttpClient>()
    .AddHttpMessageHandler<RequestHandler>();

See outgoing request middleware part of the docs.

CodePudding user response：

If you also seek to add the DelegatingHandler to all of your HttpClients constructed by the IHttpClientFactory, then the following will achieve that.

builder.Services.ConfigureAll<HttpClientFactoryOptions>(options =>
    {
        options.HttpMessageHandlerBuilderActions.Add(builder =>
        {
            builder.AdditionalHandlers.Add(builder.Services.GetRequiredService<RequestHandler>());
        });
    });
builder.Services.AddScoped<RequestHandler>();

In the code snippet, all HttpClients will use the RequestHandler as a MessageHandler, and finally remember to add the RequestHandler to the ServiceCollection as well.