PowerMVVM

Usage

Standard Commands

// command creation
Command.Create(Action action)
Command.Create(Action action, Func<bool> canExecute)
Command.Create<T>(Action<T> action)
Command.Create<T>(Action<T> action, Func<T, bool> canExecute)
Command.Create(Func<Task> action)
Command.Create<T>(Func<T, Task> action)
Command.Create(Func<Task> action, Func<bool> canExecute)
Command.Create<T>(Func<T, Task> action, Func<T, bool> canExecute)
Command.Create(ICommand command)

// command configuration
Command.Create(MyAction)
       .ContinueWith(MyContinuationAction)      // configure a continuation action
       .UseErrorHandler(MyErrorHandler)         // set an error handler
       .UseLoadingIndicator()                   // display the loading indicator (disabled by default)
       .UseLoadingIndicator(ILoadingIndicator)  // control an external loading indicator instance
       .UseLoadingIndicator(show, hide)         // control any loading states with show and hide callbacks
       .AllowMultipleExecution()                // disable the multi-execution prevention (enabled by default)
       .ContinueOncapturedContext()             // return to originating thread after command action execution (disabled by default)
       .ConfigureRaiseCanExecuteChanged(pco =>  // configure (or change) to automatically raise CanExecuteChanged
            pco.SetPropertyHolder(this)                         // when in the set view model
               .SubscribeToProperty(nameof(MyProperty))         // any of the subscribed properties change
       .AddRaiseCanExecuteChanged(pco =>        // configure to automatically raise CanExecuteChanged
            pco.SetPropertyHolder(anyViewModel)                         // when in one of the set view models
               .SubscribeToProperty(nameof(MyProperty))         // any of the subscribed properties change

// external services configuration
Command.LoggingProvider = (ILoggingProvider)provider;
Command.StatusProvider = (AStatusProvider)provider;
Command.AlwaysContinueOnCapturedContext = true;             // always return to the commands action context

Special Commands

Background Command

The special class BackgroundCommand supports long runing, CPU bound tasks. It is best used for fire-and-forget implementations, such as triggering an upload.
Cancellation, Errorhandling and Continuation Actions are supported as well. It also uses the standard logging provider (see above).
PowerMVVM.Commands.Testability provides all necessary methods to test your command's code.
Please use with care, to avoid memory leaks and strong references to your view models when the command might run for a really long time!

// background task signature
Task MyBackgroundTask(object commandParameter, CancellationToken token) { ... }

// command configuration
new BackgroundCommand(MyBackgroundTask, Func<bool> canExecute, initialConcurrentRequests, maximumConcurrentRequests);
    .ContinueWith(Action<object> continuationAction)
    .RegisterCancellationTokenFactory(Func<CancellationToken> factory)
    .SetCancellationHandler(Action cancellationHandler)
    .SetErrorHandler(Action<Exception> errorHandler)

Auto-Reset Command

The special class AutoResetCommand enables fire-once commands. Inspired by the AutoResetEvent of the framework, it just does nothing until it gets signalled. When it's time to evaluate and execute the command, it triggers exactly once, and resets itself to a non-signalled state, waiting for the next signal to wake it up.
Please note, that it will never block. It just gets ignored when not signalled.

// command configuration
new AutoResetCommand(syncOrAsyncAction)                 // creates a non signalled auto reset command
    .ContinueWith(Action continuationAction)
    .SetErrorHandler(Action<Exception> errorHandler)
    
myAutoResetCommand.Signal();    \\ tell the command, that it should run exactly one time on it's next call to execute

Customisation

Extending PowerMVVM's commands

As mentioned before, it is possible to wrap any ICommand into a command, via the given factory method. Still you can create your own commands by inheriting from the abstract base class ACommand.

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