Implicit using directives

Context: Implicit using directives automatically import common namespaces. They are enabled by default in .NET 10 projects.

When using top-level statements (or setting ImplicitUsings in .csproj), common namespaces are automatically imported.

Default Implicit Usings

SDK Type	Implicit Usings
Microsoft.NET.Sdk	System, System.Collections.Generic, System.IO, System.Linq, System.Net.Http, System.Threading, System.Threading.Tasks
Microsoft.NET.Sdk.Web	Plus ASP.NET Core namespaces
Microsoft.NET.Sdk.Worker	Plus background service namespaces

Configuration

In .csproj:

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

Disable Implicit Usings

<PropertyGroup>
  <ImplicitUsings>disable</ImplicitUsings>
</PropertyGroup>

Global Usings

Create GlobalUsings.cs:

global using System.Text.Json;
global using MyApp.Common;