Merge pull request #2907 from PrismLibrary/dev/ds/asyncdelcommand

Adding AsyncDelegateCommand

src/Prism.Core/Commands/AsyncDelegateCommand.cs

@@ -0,0 +1,225 @@
+using System.Linq.Expressions;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Windows.Input;
+using Prism.Properties;
+
+#nullable enable
+namespace Prism.Commands;
+
+/// <summary>
+/// Provides an implementation of the <see cref="IAsyncCommand"/>
+/// </summary>
+public class AsyncDelegateCommand : DelegateCommandBase, IAsyncCommand
+{
+    private bool _enableParallelExecution = false;
+    private bool _isExecuting = false;
+    private readonly Func<CancellationToken, Task> _executeMethod;
+    private Func<bool> _canExecuteMethod;
+    private Func<CancellationToken> _getCancellationToken = () => CancellationToken.None;
+
+    /// <summary>
+    /// Creates a new instance of <see cref="AsyncDelegateCommand"/> with the <see cref="Func{Task}"/> to invoke on execution.
+    /// </summary>
+    /// <param name="executeMethod">The <see cref="Func{Task}"/> to invoke when <see cref="ICommand.Execute(object)"/> is called.</param>
+    public AsyncDelegateCommand(Func<Task> executeMethod)
+        : this(c => executeMethod(), () => true)
+    {
+
+    }
+
+    /// <summary>
+    /// Creates a new instance of <see cref="AsyncDelegateCommand"/> with the <see cref="Func{Task}"/> to invoke on execution.
+    /// </summary>
+    /// <param name="executeMethod">The <see cref="Func{CancellationToken, Task}"/> to invoke when <see cref="ICommand.Execute(object)"/> is called.</param>
+    public AsyncDelegateCommand(Func<CancellationToken, Task> executeMethod)
+        : this(executeMethod, () => true)
+    {
+
+    }
+
+    /// <summary>
+    /// Creates a new instance of <see cref="DelegateCommand"/> with the <see cref="Func{Task}"/> to invoke on execution
+    /// and a <see langword="Func" /> to query for determining if the command can execute.
+    /// </summary>
+    /// <param name="executeMethod">The <see cref="Func{Task}"/> to invoke when <see cref="ICommand.Execute"/> is called.</param>
+    /// <param name="canExecuteMethod">The delegate to invoke when <see cref="ICommand.CanExecute"/> is called</param>
+    public AsyncDelegateCommand(Func<Task> executeMethod, Func<bool> canExecuteMethod)
+        : this(c => executeMethod(), canExecuteMethod)
+    {
+    }
+
+    /// <summary>
+    /// Creates a new instance of <see cref="DelegateCommand"/> with the <see cref="Func{Task}"/> to invoke on execution
+    /// and a <see langword="Func" /> to query for determining if the command can execute.
+    /// </summary>
+    /// <param name="executeMethod">The <see cref="Func{CancellationToken, Task}"/> to invoke when <see cref="ICommand.Execute"/> is called.</param>
+    /// <param name="canExecuteMethod">The delegate to invoke when <see cref="ICommand.CanExecute"/> is called</param>
+    public AsyncDelegateCommand(Func<CancellationToken, Task> executeMethod, Func<bool> canExecuteMethod)
+        : base()
+    {
+        if (executeMethod == null || canExecuteMethod == null)
+            throw new ArgumentNullException(nameof(executeMethod), Resources.DelegateCommandDelegatesCannotBeNull);
+
+        _executeMethod = executeMethod;
+        _canExecuteMethod = canExecuteMethod;
+    }
+
+    /// <summary>
+    /// Gets the current state of the AsyncDelegateCommand
+    /// </summary>
+    public bool IsExecuting
+    {
+        get => _isExecuting;
+        private set => SetProperty(ref _isExecuting, value, OnCanExecuteChanged);
+    }
+
+    ///<summary>
+    /// Executes the command.
+    ///</summary>
+    public async Task Execute(CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            IsExecuting = true;
+            await _executeMethod(cancellationToken);
+        }
+        catch (TaskCanceledException) when (cancellationToken.IsCancellationRequested)
+        {
+            // Do nothing... the Task was cancelled
+        }
+        catch (Exception ex)
+        {
+            if (!ExceptionHandler.CanHandle(ex))
+                throw;
+
+            ExceptionHandler.Handle(ex, null);
+        }
+        finally
+        {
+            IsExecuting = false;
+        }
+    }
+
+    /// <summary>
+    /// Determines if the command can be executed.
+    /// </summary>
+    /// <returns>Returns <see langword="true"/> if the command can execute,otherwise returns <see langword="false"/>.</returns>
+    public bool CanExecute()
+    {
+        try
+        {
+            if (!_enableParallelExecution && IsExecuting)
+                return false;
+
+            return _canExecuteMethod?.Invoke() ?? true;
+        }
+        catch (Exception ex)
+        {
+            if (!ExceptionHandler.CanHandle(ex))
+                throw;
+
+            ExceptionHandler.Handle(ex, null);
+
+            return false;
+        }
+    }
+
+    /// <summary>
+    /// Handle the internal invocation of <see cref="ICommand.Execute(object)"/>
+    /// </summary>
+    /// <param name="parameter">Command Parameter</param>
+    protected override async void Execute(object parameter)
+    {
+        await Execute(_getCancellationToken());
+    }
+
+    /// <summary>
+    /// Handle the internal invocation of <see cref="ICommand.CanExecute(object)"/>
+    /// </summary>
+    /// <param name="parameter"></param>
+    /// <returns><see langword="true"/> if the Command Can Execute, otherwise <see langword="false" /></returns>
+    protected override bool CanExecute(object parameter)
+    {
+        return CanExecute();
+    }
+
+    /// <summary>
+    /// Enables Parallel Execution of Async Tasks
+    /// </summary>
+    /// <returns>The current instance of <see cref="AsyncDelegateCommand"/>.</returns>
+    public AsyncDelegateCommand EnableParallelExecution()
+    {
+        _enableParallelExecution = true;
+        return this;
+    }
+
+    /// <summary>
+    /// Provides a delegate callback to provide a default CancellationToken when the Command is invoked.
+    /// </summary>
+    /// <param name="factory">The default <see cref="CancellationToken"/> Factory.</param>
+    /// <returns>The current instance of <see cref="AsyncDelegateCommand"/>.</returns>
+    public AsyncDelegateCommand CancellationTokenSourceFactory(Func<CancellationToken> factory)
+    {
+        _getCancellationToken = factory;
+        return this;
+    }
+
+    /// <summary>
+    /// Observes a property that implements INotifyPropertyChanged, and automatically calls DelegateCommandBase.RaiseCanExecuteChanged on property changed notifications.
+    /// </summary>
+    /// <typeparam name="T">The object type containing the property specified in the expression.</typeparam>
+    /// <param name="propertyExpression">The property expression. Example: ObservesProperty(() => PropertyName).</param>
+    /// <returns>The current instance of <see cref="AsyncDelegateCommand"/>.</returns>
+    public AsyncDelegateCommand ObservesProperty<T>(Expression<Func<T>> propertyExpression)
+    {
+        ObservesPropertyInternal(propertyExpression);
+        return this;
+    }
+
+    /// <summary>
+    /// Observes a property that is used to determine if this command can execute, and if it implements INotifyPropertyChanged it will automatically call DelegateCommandBase.RaiseCanExecuteChanged on property changed notifications.
+    /// </summary>
+    /// <param name="canExecuteExpression">The property expression. Example: ObservesCanExecute(() => PropertyName).</param>
+    /// <returns>The current instance of <see cref="AsyncDelegateCommand"/>.</returns>
+    public AsyncDelegateCommand ObservesCanExecute(Expression<Func<bool>> canExecuteExpression)
+    {
+        _canExecuteMethod = canExecuteExpression.Compile();
+        ObservesPropertyInternal(canExecuteExpression);
+        return this;
+    }
+
+    /// <summary>
+    /// Provides the ability to connect a delegate to catch exceptions encountered by CanExecute or the Execute methods of the DelegateCommand
+    /// </summary>
+    /// <param name="catch">TThe callback when a specific exception is encountered</param>
+    /// <returns>The current instance of <see cref="AsyncDelegateCommand"/>.</returns>
+    public AsyncDelegateCommand Catch<TException>(Action<TException> @catch)
+        where TException : Exception
+    {
+        ExceptionHandler.Register<TException>(@catch);
+        return this;
+    }
+
+    /// <summary>
+    /// Provides the ability to connect a delegate to catch exceptions encountered by CanExecute or the Execute methods of the DelegateCommand
+    /// </summary>
+    /// <param name="catch">The generic / default callback when an exception is encountered</param>
+    /// <returns>The current instance of <see cref="AsyncDelegateCommand"/>.</returns>
+    public AsyncDelegateCommand Catch(Action<Exception> @catch)
+    {
+        ExceptionHandler.Register<Exception>(@catch);
+        return this;
+    }
+
+    Task IAsyncCommand.ExecuteAsync(object? parameter)
+    {
+        return Execute(_getCancellationToken());
+    }
+
+    Task IAsyncCommand.ExecuteAsync(object? parameter, CancellationToken cancellationToken)
+    {
+        return Execute(cancellationToken);
+    }
+}