HttpClient in ASP.NET 5.0 not found?

Finally got it all worked out. @yuval set me on the right track with his answer about adding dependencies and pointing out that the class exists on github. Further searching led me to figure out that the class doesn't seem to be included in the preview release just yet, and I had to add this nuget repo to my project:https://www.myget.org/gallery/aspnetvnext

In that repo are nightly builds of the asp.net vnext nuget packages, which contained the class I want. Adding the following line to my main dependencies section and to both frameworks dependencies sections got this working for me:"Microsoft.Net.Http.Client": "1.0.0.0-rc1-10049"

"dependencies": {    [...],    "Microsoft.Net.Http.Client": "1.0.0.0-rc1-10049"},"frameworks": {    "aspnet50": {        "dependencies": {            "Microsoft.Net.Http.Client": "1.0.0-rc1-10049"        }    },    "aspnetcore50": {        "dependencies": {            "Microsoft.Net.Http.Client": "1.0.0-rc1-10049"        }    }} 

I've encountered the same problem today and the solution has gotten somewhat simpler in 2016.

It isn't required to add a new Nuget repository any longer.

When adding System.Net.Http (current version 4.0.1-beta-23516), you will still get the same error if you are targeting a clr as well as a core framework version, so need to copy the dependency into the dnxcore framework dependency list, to get your code compiling.

Before:

"frameworks": {    "dnx451": {       "dependencies": {        "System.Net.Http": "4.0.1-beta-23516"      }     },    "dnxcore50": { }  }

After:

"frameworks": {    "dnx451": {      "dependencies": {        "System.Net.Http": "4.0.1-beta-23516"      }    },    "dnxcore50": {      "dependencies": {        "System.Net.Http": "4.0.1-beta-23516"      }    }  }

You need to add a new source to your nuget package manager (https://www.myget.org/F/aspnetvnext) and then add dependencies to your project.json file. Both for dnx451 and dnxcore50:

{   "frameworks": {       "dnx451": {         "frameworkAssemblies": {             "Microsoft.Net.Http.Client": "1.0.0-beta3-10053"              }         },         "dnxcore50": {            "frameworkAssemblies": {               "Microsoft.Net.Http.Client": "1.0.0-beta3-10053"               }          } }

It is implemented as part of the ASP.Net xNext package, as they state on github:

Fully managed HttpMessageHandler implementation based on sockets.

This project is part of ASP.NET vNext. You can find samples, documentation and getting started instructions for ASP.NET vNext at the Home repo.

A full walkthrough can be found here