Commands

Commands are be defined by methods and classes.

Using our calculator example...

public class Calculator
{
    public void Add(int value1, int value2)
    {
        Console.WriteLine($"Answer:  {value1 + value2}");
    }

    public void Subtract(int value1, int value2)
    {
        Console.WriteLine($"Answer:  {value1 - value2}");
    }
}

class Program
{
    static int Main(string[] args)
    {
        return new AppRunner<Calculator>().Run(args);
    }
}

Calculator is the root command and is not directly referenced in the terminal.

Add and Subtract are the commands.

Command methods must:

• be public
• return void, int, Task or Task<int>

Command methods may be async.

When the return type is int the value is used as the exit code.

Command Attribute

Every public method will be interpreted as a command and the command name will be the method name.

Use the [Command] attribute to change the command name, enhance help output and provide parser hints.

public class Calculator
{
    [Command(Name="sum",
        Usage="sum <int> <int>",
        Description="sums two numbers",
        ExtendedHelpText="more details and examples")]
    public void Add(int value1, int value2)
    {
        Console.WriteLine($"Answer:  {value1 + value2}");
    }
}

~
$ dotnet add.dll Add --help

dotnet example.dll sum -h
sums two numbers

Usage: sum <int> <int>

Arguments:

  value1  <NUMBER>

  value2  <NUMBER>

more details and examples

Use IgnoreUnexpectedOperands & ArgumentSeparatorStrategy to override argument parsing behavior for the command. See Argument Separator for more details.

Default Method

Let's refactor our calculator. Let's rename the application to Add with the single Add command.

public class Calculator
{
    public void Add(int value1, int value2)
    {
        Console.WriteLine($"Answer:  {value1 + value2}");
    }
}

Now executed as

dotnet add.dll Add 1 2

Notice the redundant Add command. Fix this with the [DefaultMethod] attribute.

public class Calculator
{
    [DefaultMethod]
    public void Add(int value1, int value2)
    {
        Console.WriteLine($"Answer:  {value1 + value2}");
    }
}

Now executed as

dotnet add.dll 1 2