Microsoft.Extensions.Http is a .NET library, and none of the candidate sources document it directly; the closest matches are .NET HTTP client libraries such as Flurl and RestSharp, which are not Microsoft's package. Microsoft's own page 1 does not describe this package in the source text, so the answer below is based on the HTTP client libraries that the sources do describe.

A question back: Do you want the official Microsoft.Extensions.Http package from NuGet (which the candidate sources do not describe), or would a third-party .NET HTTP client like Flurl or RestSharp do?

1. 1

   Flurlflurl.devverified and signed

   A fluent URL builder and asynchronous HTTP client library for .NET that includes a testing helper for faking and recording HTTP calls 4.

   WebsiteDocs

   for agents: httpclient · http · rest

2. 2

   RestSharprestsharp.devwebsite read, tools not yet checked

   A .NET HTTP client with async APIs, automatic XML or JSON serialization of requests and responses, and parameter helpers 8.

   WebsiteDocs