Stuck on an issue?

Lightrun Answers was designed to reduce the constant googling that comes with debugging 3rd party libraries. It collects links to all the places you might be looking at while hunting down a tough bug.

And, if you’re still stuck at the end, we’re happy to hop on a call to see how we can help out.

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

See original GitHub issue

Describe the bug

C# 10 introduces global usings. The .NET 6 SDK ships with a default template for implicit usings. For the regular SDK (e.g., non-Web), this generated C# looks like:

// <auto-generated/>
global using global::System;
global using global::System.Collections.Generic;
global using global::System.IO;
global using global::System.Linq;
global using global::System.Net.Http;
global using global::System.Threading;
global using global::System.Threading.Tasks;

However, System.Net.Http is a namespace that does not exist in .NET Framework 4.x. Therefore, this namespace should not be imported implicitly.

To Reproduce

A csproj like this will suffice:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net48</TargetFramework>
    <Nullable>enable</Nullable>
    <LangVersion>10.0</LangVersion>
    <ImplicitUsings>enable</ImplicitUsings>
  </PropertyGroup>

</Project>

This will fail to build with:

Error | CS0234 | The type or namespace name 'Http' does not exist in the namespace 'System.Net' (are you missing an assembly reference?)

Issue Analytics

State:
Created 2 years ago
Comments:6 (1 by maintainers)

Top GitHub Comments

8reactions

aprillove2858commented, Jun 6, 2022

FUCK YOU STOP BY

On Mon, Jun 6, 2022, 3:34 PM Paul Williams @.***> wrote:

<Using Remove="System.Net.Http" /> does the trick.

— Reply to this email directly, view it on GitHub https://github.com/dotnet/sdk/issues/24146#issuecomment-1147896159, or unsubscribe https://github.com/notifications/unsubscribe-auth/AXZ3LW2IOU7ANNX6EGH3RQ3VNZODXANCNFSM5PT6WVCQ . You are receiving this because you are subscribed to this thread.Message ID: @.***>

6reactions

pranavkmcommented, Mar 2, 2022

Therefore, this namespace should not be imported implicitly.

The default list of usings are primarily tailored for .NET 6 and newer apps, and aren’t enabled by default. You can use the Using itemgroup to specify a custom list of global usings to be used for your app, or use MSBuild to remove ones added by ImplicitUsings=Enable e.g. <Using Remove="System.Net.Http" />.