How to make the .net HttpClient use http 2.0?

I have an asp.net web api hosted on IIS 10 (windows server 2016). When I make a GET request to this from a Microsoft Edge browser, I see that HTTP 2.0 is used in IIS logs

2015-09-20 21:57:59 100.76.48.17 GET /RestController/Native - 443 - 73.181.195.76 HTTP/2.0 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/42.0.2311.135+Safari/537.36+Edge/12.10240 - 200 0 0 7299

However, when a GET request is made through a .net 4.6 client as below,

using (var client = new HttpClient())
{
    client.BaseAddress = new Uri("https://myapp.cloudapp.net/");

    HttpResponseMessage response = await client.GetAsync("RestController/Native");
    if (response.IsSuccessStatusCode)
    {
        await response.Content.CopyToAsync(new MemoryStream(buffer));
    }
}

I see the following HTTP 1.1 log in the server logs

2015-09-20 20:57:41 100.76.48.17 GET /RestController/Native - 443 - 131.107.160.196 HTTP/1.1 - - 200 0 0 707

How can I make the .net client use HTTP/2.0 ?

Answers:

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Method 1

1.Make sure you are on the latest version of Windows 10.

2.Install WinHttpHandler:

Install-Package System.Net.Http.WinHttpHandler

3.Extend WinHttpHandler to add http2.0 support:

public class Http2CustomHandler : WinHttpHandler
{
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
    {
        request.Version = new Version("2.0");
        return base.SendAsync(request, cancellationToken);
    }
}

4.Pass above handler to the HttpClient constructor

using (var httpClient = new HttpClient(new Http2CustomHandler()))
{
      // your custom code
}

Method 2

HttpClient does not support HTTP/2 yet. It will be available in the next release (code name KATANA). Here is the link to their source code for the next release.

Till then, you could implement your own HttpMessageHandler object that implements HTTP/2 and pass it to the HttpClient‘s constructor (you probably can use their source code from KATANA).

Method 3

In addition to WinHttpHandler (as described in Shawinder Sekhon’s answer), .NET Core 3.0 includes HTTP/2 support in the default SocketsHttpHandler (#30740). Since HTTP/1.1 is still the default, either the default must be changed by setting HttpClient.DefaultRequestVersion, or Version must be changed on each request. The version can be set when the request message is created:

using (var client = new HttpClient())
{
    client.BaseAddress = new Uri("https://myapp.cloudapp.net/");

    HttpResponseMessage response = await client.SendAsync(
        new HttpRequestMessage(HttpMethod.Get, "RestController/Native")
        {
            Version = HttpVersion.Version20,
        });
    if (response.IsSuccessStatusCode)
    {
        await response.Content.CopyToAsync(new MemoryStream(buffer));
    }
}

Or by using a custom HttpMessageHandler, such as:

public class ForceHttp2Handler : DelegatingHandler
{
    public ForceHttp2Handler(HttpMessageHandler innerHandler)
        : base(innerHandler)
    {
    }

    protected override Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, CancellationToken cancellationToken)
    {
        request.Version = HttpVersion.Version20;
        return base.SendAsync(request, cancellationToken);
    }
}

which can delegate to SocketsHttpHandler, WinHttpHandler, or any other HttpMessageHandler which supports HTTP/2:

using (var client = new HttpClient(new ForceHttp2Handler(new SocketsHttpHandler())))
{
    client.BaseAddress = new Uri("https://myapp.cloudapp.net/");

    HttpResponseMessage response = await client.GetAsync("RestController/Native");
    if (response.IsSuccessStatusCode)
    {
        await response.Content.CopyToAsync(new MemoryStream(buffer));
    }
}

Method 4

HTTP/2 looks like it will be supported in C# client calls with .NET 4.6.2

https://msdn.microsoft.com/en-us/library/ms171868(v=vs.110).aspx

HTTP/2 Support (Windows 10)

HTTP/2 is a new version of the HTTP protocol that provides much better
connection utilization (fewer round-trips between client and server),
resulting in lower latency web page loading for users. Web pages (as
opposed to services) benefit the most from HTTP/2, since the protocol
optimizes for multiple artifacts being requested as part of a single
experience. HTTP/2 support has been added to ASP.NET in the .NET
Framework 4.6. Because networking functionality exists at multiple
layers, new features were required in Windows, in IIS, and in ASP.NET
to enable HTTP/2. You must be running on Windows 10 to use HTTP/2 with
ASP.NET.

HTTP/2 is also supported and on by default for Windows 10 Universal
Windows Platform (UWP) apps that use the System.Net.Http.HttpClient
API.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0