dotnet/CommunityToolkit.Mvvm/Input/Interfaces/IAsyncRelayCommand.cs

// 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 running operations for this command can be canceled.
    /// </summary>
    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>
    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();
}