---
title: Dependency injection
description: When using Nullean.Argh.Hosting, DI integration is fully transparent. Register your handler and middleware types in the service collection and the generated...
url: https://docs-v3-preview.elastic.dev/argh/hosting/dependency-injection
---

# Dependency injection
When using `Nullean.Argh.Hosting`, DI integration is fully transparent. Register your handler and middleware types in the service collection and the generated code resolves them automatically. No manual `ServiceProvider` wiring needed.

## Handler with injected service

```csharp
public class DeployCommands(IDeployService deployer)
{
    public async Task<int> Run(string environment)
    {
        await deployer.DeployAsync(environment);
        return 0;
    }
}
```

```csharp
builder.Services.AddScoped<IDeployService, DeployService>();
builder.Services.AddArgh(args, b => b.Map<DeployCommands>());
```


## DI lifetime APIs


| API                                                          | Purpose                                                               |
|--------------------------------------------------------------|-----------------------------------------------------------------------|
| `Map<T>()`                                                   | Register `T` as transient and add all its public methods as commands. |
| `MapTransient<T>()` / `MapScoped<T>()` / `MapSingleton<T>()` | Same, with an explicit DI lifetime.                                   |
| `UseGlobalOptions<T>()`                                      | Register `T` as the global options type and add it to DI.             |
| `UseMiddleware<TMiddleware>()`                               | Register middleware as transient.                                     |
| `UseMiddleware<TMiddleware>(lifetime)`                       | Register middleware with an explicit DI lifetime.                     |


## Example with lifetimes

```csharp
using Microsoft.Extensions.DependencyInjection;

builder.Services.AddArgh(args, b =>
{
    b.MapScoped<DeployCommands>();      
    b.UseMiddleware<AuditMiddleware>(ServiceLifetime.Singleton);  
    b.Map("ping", PingHandlers.Run);   
    b.UseGlobalOptions<GlobalOptions>();
});
```


## Without hosting

<dropdown title="Advanced: using DI without Nullean.Argh.Hosting">
  For advanced use or when not using `Nullean.Argh.Hosting`: `ArghServices.ServiceProvider` is typed as `System.IServiceProvider` and set when running under a host.For `Map<T>()` instance methods and `UseMiddleware<T>()` / `[MiddlewareAttribute<T>]`, generated code resolves via `GetService(typeof(T))` when a provider is present. Otherwise it falls back to `new T()`.
</dropdown>


## AOT considerations

<warning>
  For native AOT / trimming, register handler and middleware types explicitly in DI so required constructors are preserved.
</warning>