ARC0002: Missing [Command] attribute on command-like type

Rule

Types that look like commands (properties plus Handle methods) must be marked with [Command] to be recognized as commands.

Severity

Warning

Example

Violation

public record CreateUser
{
    public string Name { get; set; }

    // ARC0002: Missing [Command] attribute
    public void Handle()
    {
        // Command logic
    }
}

Fix

[Command]
public record CreateUser
{
    public string Name { get; set; }
    public string Email { get; set; }

    public void Handle()
    {
        // Command logic
    }
}

[Command]
public record CreateUser
{
    public string Name { get; set; }

    public UserCreatedResult Handle()
    {
        return new UserCreatedResult { UserId = Guid.NewGuid() };
    }
}

Why This Rule Exists

Commands are identified by the [Command] attribute. Without it:

• Handlers are not discovered by the runtime.
• Validation and metadata generation are incomplete.
• Command routing becomes inconsistent across the system.

Related Rules

• ARC0001: Incorrect query method signature on ReadModel