System.Net.Http: missing from namespace?

Question

Here is my class so far:

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Web;
using System.Net;
using System.IO;

public class MyClass
    {
        private const string URL = "https://sub.domain.com/objects.json?api_key=123";
        private const string data = @"{""object"":{""name"":""Title""}}";

        public static void CreateObject()
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
            request.Method = "POST";
            request.ContentType = "application/json";
            request.ContentLength = data.Length;
            StreamWriter requestWriter = new StreamWriter(request.GetRequestStream(), System.Text.Encoding.ASCII);
            requestWriter.Write(data);
            requestWriter.Close();

            try
            {
                // get the response
                WebResponse webResponse = request.GetResponse();
                Stream webStream = webResponse.GetResponseStream();
                StreamReader responseReader = new StreamReader(webStream);
                string response = responseReader.ReadToEnd();
                responseReader.Close();
            }
            catch (WebException we)
            {
                string webExceptionMessage = we.Message;
            }
            catch (Exception ex)
            {
                // no need to do anything special here....
            }
        }

        static void Main(string[] args)
        {
            MyClass.CreateObject();
        }
}

When I do csc filename.cs, I get the following error:

The type or namespace name 'Http' does not exist in the namespace 'System.Net' (are you missing an assembly reference?)

I'm using .NET 4.5

You're trying to access a non-static field from a static method (the webClient field). Also, you never actually use it for anything. You could probably just remove it. — Cᴏʀʏ
– Cᴏʀʏ, Commented Mar 8, 2012 at 0:37

M.Babcock · Accepted Answer · 2015-12-18 14:34:02Z

134

HttpClient lives in the System.Net.Http namespace.

You'll need to add:

using System.Net.Http;

And make sure you are referencing System.Net.Http.dll in .NET 4.5.

The code posted doesn't appear to do anything with webClient. Is there something wrong with the code that is actually compiling using HttpWebRequest?

Update

To open the Add Reference dialog right-click on your project in Solution Explorer and select Add Reference.... It should look something like:

enter image description here

edited Dec 18, 2015 at 14:34

answered Mar 8, 2012 at 0:38

M.Babcock

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9 Comments

NullVoxPopuli Over a year ago

I just installed .NET 4.5, and it says namespace name 'Http' does not exist in the namespace 'System.Net'

M.Babcock Over a year ago

Are you sure your project is targeting .NET 4.5 and that you've added the reference to System.Net.Http.dll?

M.Babcock Over a year ago

Um... no it won't. Right click on your project in Solution Explorer and click Add References when the dialog appears, select the left most tab (I don't use the built-in references dialog but mine is called Assemblies). Scroll the list until you see an item called System.Net.Http double-click it and rebuild.

M.Babcock Over a year ago

Certainly. Here's some documentation from MSDN for doing it. Let me know if you run into any troubles.

Haymaker87 Over a year ago

Are you working in a solution with multiple projects? Are you sure that the System.Net.Http assembly is installed in the project which contains the file you're looking at? You can adjust which projects load which nuget packages in the Package Manager

|

d_f · Accepted Answer · 2020-06-17 21:04:20Z

108

NuGet > Microsoft.AspNet.WebApi.Client package

edited Jun 17, 2020 at 21:04

d_f

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answered Dec 2, 2012 at 11:25

user1662812

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4 Comments

Boinst Over a year ago

This pretty much solved the problem for me. I installed this package: nuget.org/packages/Microsoft.AspNet.WebApi.SelfHost/5.2.2

adinas Over a year ago

The accepted answer (adding a reference) didn't help me but this did. Thanks.

DarthCoder77 Over a year ago

This is the correct approach to take. Adding a reference to a dll could pose issues on a build server. Having the correct nuget package will solve the issue.

pooya13 Dec 24, 2024 at 1:21

Any ideas why this is not shipped with net framework like other system DLLs?

LagiNatoRRR · Accepted Answer · 2015-06-04 12:11:01Z

18

How I solved it.

Open project (!) "Properties", choose "Application", select targeting framework ".Net Framework 4.5"
Right click on your project -> Add reference
Make sure that in "Assemblies" -> "Extensions" option "System.Net.Http" is unchecked
Go to "Assemblies" -> "Framework" and select "System.Net.Http" and "System.Net.Http" options
That`s all!

In my case i had at the beginning .Net 4.0 and "Assemblies" -> "Extensions" option "System.Net.Http" with version 2.0.0.0. After my actions "Assemblies" -> "Framework" options "System.Net.Http" and "System.Net.Http" had the same 4.0.0.0 version.

answered Jun 4, 2015 at 12:11

LagiNatoRRR

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1 Comment

FelixJongleur42 Over a year ago

that was the problem for me as well, it was not showing Reference "System.Net.Http" until I upgraded from .NET 3.5 to .NET 4.5

lance-p · Accepted Answer · 2015-09-23 12:14:29Z

11

Visual Studio Package Manager Console > Install-Package Microsoft.AspNet.WebApi.Client

answered Sep 23, 2015 at 12:14

lance-p

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Comments

Hussein Alrubaye · Accepted Answer · 2015-09-01 14:30:06Z

7

just go to add reference then add

system.net.http

answered Sep 1, 2015 at 14:30

Hussein Alrubaye

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Comments

Ussabin · Accepted Answer · 2013-01-01 19:16:46Z

6

Assuming that your using Visual Studio 10, you can download an install that includes System.Net.Http, for Visual Studio 10 here: download MVC4 for VS10

Once you've installed it, right click on the References folder in the VS Project and then select Add Reference. Then, select the Browse tab. Navigate to the assemblies install path for the MVC4 install (usually in Program Files(x86)/Microsoft ASP.NET/ASP.NET MVC4/assemblies) and select the assembly named 'System.Net.Http.dll'. Now you can add your 'using System.Net.Http' at the top of your code and begin creating HttpClient connections.

answered Jan 1, 2013 at 19:16

Ussabin

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Comments

Ned · Accepted Answer · 2020-08-02 03:30:52Z

6

I had this issue after upgrading to .NET Framework 4.7.2. I found out that Nuget package for System.Net.Http is no longer recommended. Here are workarounds:

answered Aug 2, 2020 at 3:30

Ned

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Comments

Akhil · Accepted Answer · 2012-03-08 01:48:48Z

3

You need to have a Reference to the System.Web.Http assembly which has the HTTPClient class, your trying to use. Try adding the below line before your class declaration

using System.Web.Http;

If you still get the Error, try doing this in Visual Studio

Right click on the References folder on your project.
Select Add Reference.
Select the .NET tab (or select the Browse button if it is not a .NET Framework assembly).
Double-click the assembly containing the namespace in the error message (System.Web.Http.dll).
Press the OK button.

edited Mar 8, 2012 at 1:48

answered Mar 8, 2012 at 0:38

Akhil

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5 Comments

Akhil Over a year ago

@TheLindyHop: can you try following the steps in the updated answer?

M.Babcock Over a year ago

@Akhil - HttpClient belongs to the System.Web.Http.dll .NET 4.5 assembly (not System.Net).

NullVoxPopuli Over a year ago

How do I get the references folder to show up? I've started with just a file: outside of any project =\

Akhil Over a year ago

ok, right Click on your Project, and select Properties. You should see References on the left hand side.

M.Babcock Over a year ago

@TheLindyHop - Follow the directions in my comment. It is similar but slightly more detailed.

Brian Mains · Accepted Answer · 2012-03-08 20:49:19Z

3

You'll need a using System.Net.Http at the top.

edited Mar 8, 2012 at 20:49

Brian Mains

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answered Mar 8, 2012 at 0:37

Keith Nicholas

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Comments

Elferone · Accepted Answer · 2017-04-13 15:23:41Z

3

For me, it was getting the nuget package Microsoft.Net.Http .(https://blogs.msdn.microsoft.com/bclteam/p/httpclient/)

answered Apr 13, 2017 at 15:23

Elferone

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Comments

enraged · Accepted Answer · 2020-06-29 06:33:28Z

3

With the Nuget Package Manager install Microsoft.AspNet.WebApi.Core.

After this:

using System.Web.Http;

or if you use VB

imports System.Web.Http

answered Jun 29, 2020 at 6:33

enraged

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Comments

Kibbee · Accepted Answer · 2012-03-08 00:38:17Z

2

HttpClient is new in .net 4.5. You should probably be using HttpWebRequest.

answered Mar 8, 2012 at 0:38

Kibbee

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4 Comments

M.Babcock Over a year ago

The code included in the question already uses HttpWebRequest, not sure why they aren't using it though.

Kibbee Over a year ago

Agreed. The HTTPClient is being declared, but never being used. Very odd.

NullVoxPopuli Over a year ago

I'me having an issue including the namespace for it. using System.Net.Http; yeilds the error 'Http' does not exist in the namespace 'System.Net'

Kibbee Over a year ago

Are you sure you're using the .Net 4.5 compiler?

Nicolás Alarcón Rapela · Accepted Answer · 2019-08-31 18:54:59Z

0

To solve the problem :

Go to your solution explorer.
Right click on the project name and choose add
Select references and allow the .Net framework 4.5 to finish loading
Scroll down and select System.Net.Http and click ok.

Problem solved.

edited Aug 31, 2019 at 18:54

Nicolás Alarcón Rapela

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answered Jan 3, 2015 at 22:19

boakye_wozniac

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Comments

Goodmedalist · Accepted Answer · 2019-09-13 09:55:25Z

0

Making the "Copy Local" property True for the reference did it for me. Expand References, right-click on System.Net.Http and change the value of Copy Local property to True in the properties window. I'm using VS2019.

answered Sep 13, 2019 at 9:55

Goodmedalist

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笑先生 · Accepted Answer · 2022-12-13 08:13:03Z

0

See CS0234 'Http' does not exist in the namespace 'System.Net' when targeting .NET Fx 4.x with implicit usings.

I fixed it by installing the nuget package "System.Net.Http"

answered Dec 13, 2022 at 8:13

笑先生

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Comments

jan-seins · Accepted Answer · 2018-09-28 09:52:45Z

-1

In Visual Studio you can use nuget to load the package

Microsoft.AspNet.WebApi.WebHost

edited Sep 28, 2018 at 9:52

jan-seins

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answered Sep 28, 2018 at 8:52

Cetin Sahin

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