public AsyncCommand(Func <CancellationToken, Task <TResult> > command)
 {
     this.command       = command;
     this.cancelCommand = new CancelAsyncCommand();
 }
 public AsyncCommandParameterized(Func <CancellationToken, object, Task <TResult> > commandWithParameter, object parameter)
 {
     this.commandWithParameter = commandWithParameter;
     this.cancelCommand        = new CancelAsyncCommand();
     this.commandParameter     = parameter;
 }