/// <summary>
/// Implementation of <c>ICommand</c> that allows for asynchronous operation.
/// </summary>
public class AsyncCommandBase : ICommand
{
    /// <summary>
    /// Raises the <c>CanExecuteChanged</c> event for the command.
    /// </summary>
    /// <remarks>This method should be invoked whenever the returned value of <c>CanExecute</c> changes.</remarks>
    protected void RaiseCanExecuteChanged()
    {
        if (CanExecuteChanged != null) CanExecuteChanged(this, new EventArgs());
    }
 
    /// <summary>
    /// When overridden in a derived class, performs operations in the UI thread
    /// before beginning the background operation.
    /// </summary>
    /// <param name="parameter">The parameter passed to the <c>Execute</c> method of the command.</param>
    protected virtual void BeforeExecute(object parameter) { }
 
    /// <summary>
    /// When overridden in a derived class, performs operations in a background
    /// thread when the <c>Execute</c> method is invoked.
    /// </summary>
    /// <param name="parameter">The paramter passed to the <c>Execute</c> method of the command.</param>
    protected virtual void OnExecute(object parameter) { }
 
    /// <summary>
    /// When overridden in a derived class, performs operations when the
    /// background execution has completed.
    /// </summary>
    /// <param name="parameter">The parameter passed to the <c>Execute</c> method of the command.</param>
    /// <param name="error">The error object that was thrown during the background operation, or null if no error was thrown.</param>
    protected virtual void AfterExecute(object parameter, Exception error) { }
 
    /// <summary>
    /// Occurs when changes occur that affect whether or not the command should execute.
    /// </summary>
    public event EventHandler CanExecuteChanged;
 
 
    /// <summary>
    /// When overridden in a derived class, defines the method that determines whether the command can execute in its
    /// current state.
    /// </summary>
    /// <param name="parameter">
    /// Data used by the command. If the command does not require data to be passed,
    /// this object can be set to null.
    /// </param>
    /// <returns>True if this command can be executed; otherwise, false.</returns>
    public virtual bool CanExecute(object parameter)
    {
        return true;
    }
 
    /// <summary>
    /// Runs the command method in a background thread.
    /// </summary>
    /// <param name="parameter">
    /// Data used by the command. If the command does not require data to be passed,
    /// this object can be set to null.
    /// </param>
    public void Execute(object parameter)
    {
        BeforeExecute(parameter);
 
        var bgw = new BackgroundWorker();
 
        bgw.DoWork += (s, e) =>
        {
            OnExecute(parameter);
        };
        bgw.RunWorkerCompleted += (s, e) =>
        {
            AfterExecute(parameter, e.Error);
        };
        bgw.RunWorkerAsync();
    }
}