public async Task Test_AsyncRelayCommand_WithCancellation()
{
TaskCompletionSource <object> tcs = new TaskCompletionSource <object>();
var command = new AsyncRelayCommand(token => tcs.Task);
Assert.IsTrue(command.CanExecute(null));
Assert.IsTrue(command.CanExecute(new object()));
Assert.IsTrue(command.CanBeCanceled);
Assert.IsFalse(command.IsCancellationRequested);
command.Execute(null);
Assert.IsFalse(command.IsCancellationRequested);
command.Cancel();
Assert.IsTrue(command.IsCancellationRequested);
tcs.SetResult(null);
await command.ExecutionTask !;
Assert.IsTrue(command.IsCancellationRequested);
}
public async Task Test_AsyncRelayCommand_WithCancellation()
{
TaskCompletionSource <object> tcs = new TaskCompletionSource <object>();
// We need to test the cancellation support here, so we use the overload with an input
// parameter, which is a cancellation token. The token is the one that is internally managed
// by the AsyncRelayCommand instance, and canceled when using IAsyncRelayCommand.Cancel().
var command = new AsyncRelayCommand(token => tcs.Task);
List <PropertyChangedEventArgs> args = new List <PropertyChangedEventArgs>();
command.PropertyChanged += (s, e) => args.Add(e);
// We have no canExecute parameter, so the command can always be invoked
Assert.IsTrue(command.CanExecute(null));
Assert.IsTrue(command.CanExecute(new object()));
// The command isn't running, so it can't be canceled yet
Assert.IsFalse(command.CanBeCanceled);
Assert.IsFalse(command.IsCancellationRequested);
// Start the command, which will return the token from our task completion source.
// We can use that to easily keep the command running while we do our tests, and then
// stop the processing by completing the source when we need (see below).
command.Execute(null);
// The command is running, so it can be canceled, as we used the token overload
Assert.IsTrue(command.CanBeCanceled);
Assert.IsFalse(command.IsCancellationRequested);
// Validate the various event args for all the properties that were updated when executing the command
Assert.AreEqual(args.Count, 4);
Assert.AreEqual(args[0].PropertyName, nameof(IAsyncRelayCommand.IsCancellationRequested));
Assert.AreEqual(args[1].PropertyName, nameof(IAsyncRelayCommand.ExecutionTask));
Assert.AreEqual(args[2].PropertyName, nameof(IAsyncRelayCommand.IsRunning));
Assert.AreEqual(args[3].PropertyName, nameof(IAsyncRelayCommand.CanBeCanceled));
command.Cancel();
// Verify that these two properties raised notifications correctly when canceling the command too.
// We need to ensure all command properties support notifications so that users can bind to them.
Assert.AreEqual(args.Count, 6);
Assert.AreEqual(args[4].PropertyName, nameof(IAsyncRelayCommand.IsCancellationRequested));
Assert.AreEqual(args[5].PropertyName, nameof(IAsyncRelayCommand.CanBeCanceled));
Assert.IsTrue(command.IsCancellationRequested);
// Complete the source, which will mark the command as completed too (as it returned the same task)
tcs.SetResult(null);
await command.ExecutionTask !;
// Verify that the command can no longer be canceled, and that the cancellation is
// instead still true, as that's reset when executing a command and not on completion.
Assert.IsFalse(command.CanBeCanceled);
Assert.IsTrue(command.IsCancellationRequested);
}