How to Create a New Command

1. Implement ICommand - A Command must implement the ICommand interface.
2. Add a class attribute - A class attribute may be used to add more configuration values.
3. Add command parameters - Add properties which will be populated with the values provided by the user.

The Command attribute is optional and may provide additional information and constraints about the command:

• Command Name
  • Case insensitive.
  • If provided, the command will be executed only if the verb from the generic model matches this value.
• Short Description
  • This value is displayed by the help command.

1) Create a class

• Implement the ICommand interface.

internal class ReadCommand : ICommand
{
  	public Task Execute()
  	{
  		...
  	}
}

• It may be internal.

2) Use a class attribute

The a command attribute is optional, but, if provided, it allows to specify some information about the command. There are two attributes that can be used:

• NamedCommandAttribute
• DefaultCommandAttribute

The NamedCommandAttribute

[NamedCommand("read", Description = "Reads the content of the specified file.")]
internal class ReadCommand : ICommand
{
	...
}

Allows to specify the following information for the command:

• Name

  • This is the text used in the console by the user to execute the command.
  • If no name is provided or the entire CommandAttribute is missing, than the name of the command is considered to be the name of the class. The trailing "Command" text from the name, if present, it is ignored. (Similar to ASP.NET)

• Description

  • This will be displayed to the user in the help.

• Order

  • This is the order in which will displayed by the help command.

  • Default value: 0

• Enabled

  • If the command is disabled, it will not be executed and it will not be displayed by the help command.
  • Default value: true

The DefaultCommandAttribute

The command marked with this attribute, will be the one executed when no specific command name is provided.

[DefaultCommand(Order = 100, Description = "Default command to be executed when no command name is specified.")]
internal class DefaultCommand : ICommand
{
	...
}

It has all the properties provided by the NamedCommandAttribute except the Name

3) Add Parameters

When a property of the command class is marked with a parameter attribute, it will automatically be populated with the corresponding argument value provided by the user.

There are two types of parameters:

• NamedParameterAttribute
• AnonymousParameterAttribute

The NamedParameterAttribute

[NamedCommand("read", Description = "Display the content of a text file.")]
public class ReadFileCommand : ICommand
{
    [NamedParameter("encoding", ShortName = 'e', IsOptional = true, Description = "Encoding to be used ...")]
    public Encoding Encoding { get; set; }

	public Task Execute()
	{
		...
	}
}

The AnonymousParameterAttribute

[NamedCommand("read", Description = "Display the content of a text file.")]
public class ReadFileCommand : ICommand
{
    [AnonymousParameter(Order = 1, Description = "The path to the file that should be displayed.")]
    public string FilePath { get; set; }
    
	public Task Execute()
	{
		...
	}
}