CSharp 10 Features

Last Updated: 3/17/2022

global modifier

  • The global using directive was added in C# 10
  • Adding the global modifier to a using directive means that using is applied to all files in the compilation (typically a project).

global using System

Rules

global using directives must appear before

  • All using directives without the global modifier.
  • All namespace and type declarations in the file.
  • The order of global using directives doesn't matter, either in a single file, or between files.

File

You can put global usings in any .cs file, including Program.cs or a specifically named file like globalusings.cs.

With Static modifier

The global modifier may be combined with the static modifier.

Declare

global using static System.Math;

Use

Console.WriteLine(Round(2.5678));

instead of

Console.WriteLine(Math.Round(2.5678));

Adding static, imports a type and makes the type’s members and nested types available throughout your project.

With Alias

The global modifier may be applied to a using alias directive.

Declare

global using Env = System.Environment;

Use

Console.WriteLine(Env.OSVersion);

instead of

Console.WriteLine(System.Environment.OSVersion);

In Project File

You can also globally include a namespace by adding a <Using> item to your project file

<Using Include="System.IO" />

Implicit global using

Implicit global using directives are added in new C# projects to a generated file in the project's obj directory.

Implicit global using directives are added for projects that use one of the following SDKs:

  • Microsoft.NET.Sdk
  • Microsoft.NET.Sdk.Web
  • Microsoft.NET.Sdk.Worker
  • Microsoft.NET.Sdk.WindowsDesktop

Default Namespaces for Microsoft.Net.Sdk

  • System
  • System.Collections.Generic
  • System.IO
  • System.Linq
  • System.Net.Http
  • System.Threading
  • System.Threading.Tasks

Enable ImplicitUsing

To enable implicit usings set the ImplicitUsings property in your .csproj file:

<PropertyGroup>
    <ImplicitUsings>enable</ImplicitUsings>
</PropertyGroup>

References

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