OhUsings

Import all missing C# using directives in Visual Studio — in one click.

Stop hunting for namespaces one red squiggle at a time. OhUsings scans your C# file (or your entire project/solution), resolves every missing type through Roslyn, and adds all safe using directives at once — sorted, formatted, and ready to go.

Why OhUsings?

If you've ever opened a C# file full of unresolved types and found yourself pressing Ctrl+. over and over, you know the pain. Visual Studio's built-in "Add using" handles one type at a time. JetBrains Rider has "Import Missing References," but that requires switching IDEs.

OhUsings brings that workflow to Visual Studio — with a safety-first approach that never guesses when a type is ambiguous.

Features

Feature	Description
One-Click Import	Adds all unambiguous `using` directives in a single operation
Three Scopes	Run on the current file, the active project, or the entire solution
Light Bulb Actions	Suggested actions appear inline — pick a namespace right from the editor
Ambiguity Dialog	When a type maps to multiple namespaces, a picker lets you choose
Sorted & Formatted	`System.*` namespaces first, alphabetically sorted, Roslyn-formatted
10+ Diagnostics	Handles CS0246, CS0103, CS0234, CS1061, CS1935, and more
Extension Methods	Detects missing `using` for LINQ and other extension methods
Privacy-First	Zero telemetry, zero network calls — ever

Quick Start

Install

From Visual Studio Marketplace (recommended)

Open Visual Studio 2022.
Go to Extensions → Manage Extensions.
Search for OhUsings.
Click Download and restart Visual Studio.

Or install directly from: Visual Studio Marketplace

From VSIX (local build)

Build the solution in Visual Studio 2022 (17.0+).
Locate OhUsings.vsix in the bin/ output.
Double-click the .vsix file to install.
Restart Visual Studio.

Use

Option A — Menu command

Open a C# file with unresolved types.
Go to Tools → OhUsings: Import All Missing Usings.
Done. Check the status bar for a summary.

Option B — Context menu

Right-click in the editor → OhUsings: Import All Missing Usings.

Option C — Light bulb

Place the caret on an unresolved type. Click the light bulb (or press Ctrl+.) and choose from the OhUsings suggested actions.

Handling Ambiguous Types

When a type like Timer exists in multiple namespaces (System.Timers, System.Threading), OhUsings skips it during automatic import and opens the Ambiguous Usings Dialog so you can choose.

How It Works

┌─────────────────────────┐
│  You invoke the command  │
└────────────┬────────────┘
             ▼
┌─────────────────────────┐
│  ActiveDocumentService   │  Locates the Roslyn Document(s) for the scope
└────────────┬────────────┘
             ▼
┌─────────────────────────┐
│  MissingUsingsAnalyzer   │  Reads compiler diagnostics, extracts type
│                          │  names, resolves namespaces via SymbolFinder
└────────────┬────────────┘
             ▼
        ┌────┴─────┐
   Unambiguous   Ambiguous
        │            │
        ▼            ▼
┌──────────────┐ ┌───────────────┐
│ Auto-applied │ │ Reported /    │
│ via Applier  │ │ Dialog shown  │
└──────┬───────┘ └───────────────┘
       ▼
┌─────────────────────────┐
│  UsingDirectiveApplier   │  Inserts, sorts, formats, applies changes
└────────────┬────────────┘
             ▼
┌─────────────────────────┐
│  NotificationService     │  Status bar + Output Window summary
└─────────────────────────┘

Under the hood, OhUsings uses Roslyn's semantic model — not regex or text matching — to detect unresolved types and resolve namespaces. This means zero false positives from names that are already in scope.

Supported Diagnostics

ID	Meaning	Handling
CS0246	Type or namespace not found	Primary — full resolution
CS0103	Name does not exist in current context	Full resolution
CS0234	Type/namespace does not exist in namespace	Full resolution
CS0305, CS0308	Generic type errors	Full resolution
CS0400, CS0426, CS0616	Type errors	Full resolution
CS1503, CS8179	Argument/type mismatch errors	Full resolution
CS1061, CS1929	Missing extension methods	Extension method search
CS1935	Missing query pattern	Auto-suggests `System.Linq`

Configuration

OhUsings includes a lightweight options system:

Option	Default	Description
`SortUsings`	`true`	Sort `using` directives alphabetically after adding
`PlaceSystemFirst`	`true`	Place `System.*` namespaces before third-party ones
`MaxDiagnosticsPerDocument`	`200`	Cap on diagnostics processed per file (performance guard)

Limitations

Resolves types only from assemblies already referenced by the project.
Does not add NuGet packages or project references (yet — see roadmap).
Ambiguous imports require manual resolution via the dialog or light bulb.

Architecture

The codebase follows a clean, interface-based design with four core services behind abstractions. See docs/architecture.md for the full breakdown.

Roadmap

Key planned features include a configurable keyboard shortcut, solution-wide preview/diff, NuGet package suggestions, and global usings support. See docs/roadmap.md for the complete plan.

Contributing

Contributions are welcome!

Fork the repository.
Create a feature branch: git checkout -b feature/my-feature.
Make your changes with tests.
Ensure the solution builds and all tests pass.
Submit a pull request.

Development Setup

Requirement	Details
IDE	Visual Studio 2022 with the Visual Studio extension development workload
Framework	.NET Framework 4.7.2+
APIs	Roslyn (via VS SDK)

Running Tests

Open Test Explorer in Visual Studio and run all tests, or use the CLI:

dotnet test tests/OhUsings.Tests/OhUsings.Tests.csproj

Code Style

Follow the .editorconfig rules.
Keep classes small and focused.
Add XML doc comments for public APIs.

License

MIT — see LICENSE for details.

Made with ☕ by Mabrouk Mahdhi and Wiem Ksaier