RelayCommand vs. Simplified ICommand: Which is Best for MVVM?

Detailed explanation of RelayCommand pattern in simplified MVVM implementation

In MVVM (Model-View-ViewModel) architecture, creating multiple commands can be a tedious task. This problem has prompted various solutions, including a simplified approach using a single ICommand class.

Simplified command implementation

The implemented ICommand class contains two delegate methods: OnExecute (returns void) and OnCanExecute (returns bool). In the constructor, these methods are passed as parameters. The CanExecute and Execute methods of the ICommand interface call the corresponding delegate methods.

Advantages of simplified commands

• Reduced coding effort compared to creating multiple ICommand classes.
• Commands can be flexibly defined in the ViewModel class.

Explore alternatives: RelayCommand

A common alternative to simplifying commands is the RelayCommand, as demonstrated by Karl Shifflet. It uses Action to perform specific actions, allowing for a cleaner implementation.

Implementation of RelayCommand

RelayCommand uses Predicate

Advantages of RelayCommand

• Automatically provide property change notifications for bound commands.
• Supports parameterization via delegate parameters.

Usage Example

Simplified commands and RelayCommand can be used in a similar way in ViewModel:

<code>public class MyViewModel
{
    // 简化命令
    public ICommand DoSomethingCommand { get; set; }

    // RelayCommand
    public ICommand DoSomethingCommand2 { get; set; }

    public MyViewModel()
    {
        // 简化命令
        DoSomethingCommand = new TestCommand(CanDoSomething, DoSomeImportantMethod);

        // RelayCommand
        DoSomethingCommand2 = new RelayCommand(CanDoSomething, DoSomeImportantMethod);
    }

    // ...
}</code>

Conclusion

While RelayCommand provides a neat solution, RelayCommand offers additional benefits such as automatic property change notification and parameter support. Both methods can effectively simplify the implementation of MVVM commands, allowing developers to focus on application logic rather than boilerplate code.

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