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.NET-Community-Toolkit/CommunityToolkit.Mvvm/Input/Interfaces/IAsyncRelayCommand.cs

78 lines
3.5 KiB
C#

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.ComponentModel;
using System.Threading.Tasks;
namespace CommunityToolkit.Mvvm.Input;
/// <summary>
/// An interface expanding <see cref="IRelayCommand"/> to support asynchronous operations.
/// </summary>
public interface IAsyncRelayCommand : IRelayCommand, INotifyPropertyChanged
{
/// <summary>
/// Gets the last scheduled <see cref="Task"/>, if available.
/// This property notifies a change when the <see cref="Task"/> completes.
/// </summary>
Task? ExecutionTask { get; }
/// <summary>
/// Gets a value indicating whether a running operation for this command can currently be canceled.
/// </summary>
/// <remarks>
/// The exact sequence of events that types implementing this interface should raise is as follows:
/// <list type="bullet">
/// <item>
/// The command is initially not running: <see cref="IsRunning"/>, <see cref="CanBeCanceled"/>
/// and <see cref="IsCancellationRequested"/> are <see langword="false"/>.
/// </item>
/// <item>
/// The command starts running: <see cref="IsRunning"/> and <see cref="CanBeCanceled"/> switch to
/// <see langword="true"/>. <see cref="IsCancellationRequested"/> is set to <see langword="false"/>.
/// </item>
/// <item>
/// If the operation is canceled: <see cref="CanBeCanceled"/> switches to <see langword="false"/>
/// and <see cref="IsCancellationRequested"/> switches to <see langword="true"/>.
/// </item>
/// <item>
/// The operation completes: <see cref="IsRunning"/> and <see cref="CanBeCanceled"/> switch
/// to <see langword="false"/>. The state of <see cref="IsCancellationRequested"/> is undefined.
/// </item>
/// </list>
/// This only applies if the underlying logic for the command actually supports cancelation. If that is
/// not the case, then <see cref="CanBeCanceled"/> and <see cref="IsCancellationRequested"/> will always remain
/// <see langword="false"/> regardless of the current state of the command.
/// </remarks>
bool CanBeCanceled { get; }
/// <summary>
/// Gets a value indicating whether a cancelation request has been issued for the current operation.
/// </summary>
bool IsCancellationRequested { get; }
/// <summary>
/// Gets a value indicating whether the command currently has a pending operation being executed.
/// </summary>
bool IsRunning { get; }
/// <summary>
/// Provides a more specific version of <see cref="System.Windows.Input.ICommand.Execute"/>,
/// also returning the <see cref="Task"/> representing the async operation being executed.
/// </summary>
/// <param name="parameter">The input parameter.</param>
/// <returns>The <see cref="Task"/> representing the async operation being executed.</returns>
/// <exception cref="System.ArgumentException">Thrown if <paramref name="parameter"/> is incompatible with the underlying command implementation.</exception>
Task ExecuteAsync(object? parameter);
/// <summary>
/// Communicates a request for cancelation.
/// </summary>
/// <remarks>
/// If the underlying command is not running, or if it does not support cancelation, this method will perform no action.
/// Note that even with a successful cancelation, the completion of the current operation might not be immediate.
/// </remarks>
void Cancel();
}