---
title: CancellationToken
description: Add System.Threading.CancellationToken as a parameter of your command handler method. It is not parsed from the command line and does not appear in --help...
url: https://docs-v3-preview.elastic.dev/argh/features/cancellation
---

# CancellationToken
Add `System.Threading.CancellationToken` as a parameter of your command handler method. It is not parsed from the command line and does not appear in `--help`. The source generator injects the token the runtime uses for cooperative cancellation.

## Handler injection

```csharp
public static async Task<int> Sync(
    string source,
    CancellationToken cancellationToken)
{
    await CopyTreeAsync(source, cancellationToken);
    return 0;
}
// myapp sync --source ./data   (CancellationToken is not a CLI option)
```


## DTO injection

You can also add it on an `[AsParameters]` type as a primary constructor parameter or `init` property:
```csharp
public record RunArgs(string Source, int Port, CancellationToken Ct);

public static async Task<int> Run([AsParameters] RunArgs args)
{
    await Task.Delay(1, args.Ct);
    return 0;
}
```

<tip>
  Keep CLI-bound members first in declaration order. All `[Argument]` positionals must precede flags, and `CancellationToken` must not appear between a flag and a later positional. Put the token **last** on the DTO.
</tip>


## Behavior by runtime

<tab-set>
  <tab-item title="Console app (ArghApp)">
    The token is cancelled when the user presses **Ctrl+C** (and on Windows, the console break signal). The process keeps running after cancel unless your handler exits. Argh only forwards cancellation to your code.
  </tab-item>

  <tab-item title="Hosted app (Nullean.Argh.Hosting)">
    The same console token is linked with `IHostApplicationLifetime.ApplicationStopping`, so the parameter also cancels when the host is shutting down.
  </tab-item>

  <tab-item title="TryParseArgh / TryParseDto">
    Injected `CancellationToken` members are set to `default`. There is no host or console token in that API, so the value is non-cancellable.
  </tab-item>
</tab-set>