Difference between Delegatecommand, relaycommand and routedcommand

I'm confused about command pattern. There are so many different explanations about the commands. I thought the code below was delegatecommand, but after reading about the relaycommand, I am in doubt.

What is the difference between relaycommand, delegatecommand and routedcommand. Is it possible to show in examples that have relevance to my posted code?

class FindProductCommand : ICommand
{
    ProductViewModel _avm;

    public FindProductCommand(ProductViewModel avm)
    {
        _avm = avm;
    }

    public bool CanExecute(object parameter)
    {
        return _avm.CanFindProduct();
    }

    public void Execute(object parameter)
    {
        _avm.FindProduct();
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

}

Answers


Your FindProductCommand class implements the ICommand interface, which means it can be used as a WPF command. It is neither a DelegateCommand nor a RelayCommand, nor is it a RoutedCommand, which are other implementations of the ICommand interface.


FindProductCommand vs DelegateCommand/RelayCommand

Generally, when an implementation of ICommand is named DelegateCommand or RelayCommand, the intention is that you don't have to write a class that implements the ICommand interface; rather, you pass the necessary methods as parameters to the DelegateCommand / RelayCommand constructor.

For example, instead of your entire class, you could write:

ProductViewModel _avm;
var FindPoductCommand = new DelegateCommand<object>(
    (parameter) => _avm.FindProduct(),
    (parameter) => _avm.CanFindProduct()
);

Some implementations of DelegateCommand / RelayCommand:

Related:


FindProductCommand vs RoutedCommand

Your FindProductCommand will execute FindProduct when triggered.

WPF's built-in RoutedCommand does something else: it raises a routed event which can be handled by other objects in the visual tree. This means you can attach a command binding to those other objects to execute FindProduct, while attaching the RoutedCommand itself specifically to one or more objects that trigger the command, e.g. a button, a menu item, or a context menu item.

Some related SO answers:


Need Your Help

C#: Immutable view of a list's objects?

c# immutability

I have a list, and I want to provide read-only access to a collection containing its contents. How can I do this?

Nested arguments not compiling

python python-3.x compatibility python-2.x

I'm trying to compile my code into a Python 3 module. It runs fine when I choose "Run module" in IDLE, but receive the following syntax error when I try to create a distribution: