How to add multiple HttpMessageHandler to HttpClient without HttpClientFactory

Question

I have a console application that uses HttpClient to make web requests.

var client = new HttpClient();

I'm trying to add multiple HttpMessageHandler to it (custom implementations of DelegatingHandler, really) but the constructor for HttpClient only takes a single HttpMessageHandler.

class LoggingHandler : DelegatingHandler { //... }
class ResponseContentProcessingHandler : DelegatingHandler { //... }

this is ok...

var client = new HttpClient(new LoggingHandler()); // OK

but this doesn't compile:

var client = new HttpClient(
                new LoggingHandler(), 
                new ResponseContentProcessingHandler()); // Sadness

Because I'm targeting .NET 4.0, I cannot use HttpClientFactory, which is how the solution to this problem is commonly explained:

HttpClient client = HttpClientFactory.Create(
                       new LoggingHandler(),
                       new ResponseContentProcessingHandler());

Because I'm just in a console application, rather than in an ASP.NET application, I can't do this either:

GlobalConfiguration.Configuration
                   .MessageHandlers
                   .Add(new LoggingHandler()
                   .Add(new ResponseContentProcessingHandler());

I've looked at the source for HttpClientFactory and there doesn't seem to be anything in there that wouldn't compile in .NET 4.0, but short of rolling my own factory ("inspired" by Microsoft's source code), is there a way to manually add many HTTP message handlers to the HttpClient?

Answer 1

DelegatingHandler has a protected constructor that takes a handler for the inner handler. If you have control over all your custom handlers, I would think you can add a public constructor that calls the protected constructor, like:

public class CustomHandler : DelegatingHandler
{
    public CustomHandler(HttpMessageHandler innerHandler) : base(innerHandler)
    {
    }
}

and chain them thus:

var client = new HttpClient(
    new CustomHandler(
        new OtherCustomerHandler(
            new HttpClientHandler()
        )
    )
);