> ## Documentation Index > Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt > Use this file to discover all available pages before exploring further. # C# Global Using Directive The `global using` directive, introduced in C# 10, instructs the compiler to apply a namespace import, static import, or alias across all source files within an entire compilation unit. By defining a dependency globally, the specified namespace or type becomes implicitly available to every `.cs` file in the project during the compilation process. ## Syntax Variations The `global` modifier can be applied to all three standard forms of the `using` directive: ```csharp theme={"dark"} // 1. Standard namespace import global using System.Collections.Generic; // 2. Static import (imports static members of a specific type) global using static System.Console; // 3. Aliasing (creates a global alias for a namespace or type) global using JsonDict = System.Collections.Generic.Dictionary; ``` ## Lexical Placement and Rules To ensure successful compilation, `global using` directives are subject to strict ordering rules within the source file they inhabit: 1. **Top-Level Precedence:** A `global using` directive must precede all non-global `using` directives, `namespace` declarations, and type definitions within the file. 2. **File Independence:** The directive can be placed in any `.cs` file within the project. The compiler aggregates all global usings across the compilation unit before resolving types. 3. **Redundancy Handling:** If a namespace is imported globally, declaring a standard `using` directive for the same namespace in an individual file is syntactically valid but redundant; the compiler will safely ignore the duplicate. **Valid Ordering:** ```csharp theme={"dark"} global using System.Text; global using static System.Math; using System.IO; // Non-global must come after global namespace ApplicationCore; // Type definitions follow... ``` **Invalid Ordering (Compilation Error CS8915):** ```csharp theme={"dark"} using System.IO; global using System.Text; // Error: global using must precede non-global using ``` ## MSBuild Integration (Implicit Usings) The .NET SDK leverages the `global using` feature at the build level via the `` property in the `.csproj` file. ```xml theme={"dark"} enable ``` When enabled, the MSBuild process automatically generates a file named `.GlobalUsings.g.cs` in the `obj/Debug/netX.0/` directory. This auto-generated file contains a predefined set of `global using` directives based on the project's SDK type (e.g., `Microsoft.NET.Sdk` vs `Microsoft.NET.Sdk.Web`), injecting foundational namespaces into the compilation unit without requiring manual source code declarations.

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