---
title: Command registration
description: Bind a command name to a delegate, either a method group or a lambda: The command name determines the CLI invocation path: myapp deploy …, myapp greet...
url: https://docs-v3-preview.elastic.dev/argh/commands/registration
---

# Command registration
## Map(name, handler)

Bind a command name to a delegate, either a method group or a lambda:
```csharp
app.Map("deploy", DeployHandlers.Run);
app.Map("greet", (string name) => Console.WriteLine($"Hello, {name}!"));
```

The command name determines the CLI invocation path: `myapp deploy …`, `myapp greet …`.

## MapT()

Register every public method on `T` as a command. Method names are converted to kebab-case:
```csharp
app.Map<StorageHandlers>();
```

If `StorageHandlers` has methods `List()` and `Upload(string path)`, this creates commands `myapp list` and `myapp upload --path …`.

## MapRoot(handler)

Define a default handler when no subcommand is given:
```csharp
app.MapRoot(Handlers.DefaultAction);
```

At the app level this handles bare `myapp` invocations. Inside a `MapNamespace` callback, it handles `myapp <namespace>` without a subcommand.
When using `MapRoot`, the XML doc on the handler method becomes the app-level overview in `--help`:
```csharp
/// <summary>Manage and deploy your application's cloud resources.</summary>
/// <remarks>
/// Run <c>myapp &lt;command&gt; --help</c> for details on any command.
/// </remarks>
public static Task<int> Root() { … }

app.MapRoot(Root);
```


## UseCliDescription

For apps with no default root command, use `UseCliDescription` to set a plain one-liner shown beneath the `Usage:` line:
```csharp
app.UseCliDescription("Manage and deploy your application's cloud resources.");
```

<note>
  `UseCliDescription` is on `IArghRootBuilder` (not `IArghBuilder`), so it is unavailable inside `MapNamespace` configure callbacks.
</note>

<warning>
  `UseCliDescription` cannot be combined with `MapRoot`. The generator reports `AGH0023` if both are present.
</warning>