System.Net.Http: missing from namespace? (using .net 4.5)

M

16

129

TL; DR: I'm new to this language and have no idea what I'm doing

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?)

Muffler answered 8/3, 2012 at 0:33 Comment(1)

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. – Chan 8/3, 2012 at 0:37

E

133

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

Ejaculatory answered 8/3, 2012 at 0:38 Comment(9)

I just installed .NET 4.5, and it says namespace name 'Http' does not exist in the namespace 'System.Net' – Muffler 8/3, 2012 at 1:23

Are you sure your project is targeting .NET 4.5 and that you've added the reference to System.Net.Http.dll? – Ejaculatory 8/3, 2012 at 1:24

I'm not sure, it's just one .cs file. =\ So... do I still need to add a reference to that file? Shouldn't it just auto pick the latest? – Muffler 8/3, 2012 at 1:29

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. – Ejaculatory 8/3, 2012 at 1:33

Updated answer to include directions to open the Add Reference... dialog. – Ejaculatory 8/3, 2012 at 2:4

ok, i've gotten to that menu only to realize visual studio is still using .net 4.0. is changing it to 4.5 straightforward? – Muffler 8/3, 2012 at 13:40

Certainly. Here's some documentation from MSDN for doing it. Let me know if you run into any troubles. – Ejaculatory 8/3, 2012 at 13:50

Shouldnøt it be System.Web.Http instead of System.Net.Http? – Aron 15/4, 2014 at 8:9

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 – Undesigning 3/8, 2015 at 22:6

G

108

NuGet > Microsoft.AspNet.WebApi.Client package

Grizel answered 2/12, 2012 at 11:25 Comment(3)

This pretty much solved the problem for me. I installed this package: nuget.org/packages/Microsoft.AspNet.WebApi.SelfHost/5.2.2 – Nealson 11/10, 2014 at 6:56

The accepted answer (adding a reference) didn't help me but this did. Thanks. – Fulcrum 30/12, 2015 at 9:15

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. – Jeroboam 16/3, 2018 at 16:52

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17

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.

Nara answered 4/6, 2015 at 12:11 Comment(1)

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 – Pogge 29/1, 2019 at 13:7

A

11

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

Anarthrous answered 23/9, 2015 at 12:14 Comment(0)

A

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.

Acidhead answered 1/1, 2013 at 19:16 Comment(0)

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6

just go to add reference then add

system.net.http

Inhesion answered 1/9, 2015 at 14:30 Comment(0)

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4

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:

Success answered 2/8, 2020 at 3:30 Comment(0)

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3

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

Napoleonnapoleonic answered 8/3, 2012 at 0:37 Comment(0)

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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.

Giulietta answered 8/3, 2012 at 0:38 Comment(5)

@TheLindyHop: can you try following the steps in the updated answer? – Giulietta 8/3, 2012 at 1:43

@Giulietta - HttpClient belongs to the System.Web.Http.dll .NET 4.5 assembly (not System.Net). – Ejaculatory 8/3, 2012 at 1:48

How do I get the references folder to show up? I've started with just a file: outside of any project =\ – Muffler 8/3, 2012 at 1:55

ok, right Click on your Project, and select Properties. You should see References on the left hand side. – Giulietta 8/3, 2012 at 1:58

@TheLindyHop - Follow the directions in my comment. It is similar but slightly more detailed. – Ejaculatory 8/3, 2012 at 1:58

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3

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

Mccauley answered 13/4, 2017 at 15:23 Comment(0)

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2

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

Psychrometer answered 8/3, 2012 at 0:38 Comment(4)

The code included in the question already uses HttpWebRequest, not sure why they aren't using it though. – Ejaculatory 8/3, 2012 at 0:46

Agreed. The HTTPClient is being declared, but never being used. Very odd. – Psychrometer 8/3, 2012 at 0:51

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' – Muffler 8/3, 2012 at 1:25

Are you sure you're using the .Net 4.5 compiler? – Psychrometer 8/3, 2012 at 2:15

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2

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

Leptosome answered 29/6, 2020 at 6:33 Comment(0)

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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.

Overfill answered 3/1, 2015 at 22:19 Comment(0)

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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.

Plataea answered 13/9, 2019 at 9:55 Comment(0)

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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"

Nonsmoker answered 13/12, 2022 at 8:13 Comment(0)

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-1

In Visual Studio you can use nuget to load the package

Microsoft.AspNet.WebApi.WebHost

Mohammed answered 28/9, 2018 at 8:52 Comment(0)

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