ICommand in Silverlight

let's see an instance that is easily and  can run well

  public class OpenChildWindowCommand : ICommand

    {

        /// <summary>

        /// 当出现影响是否应执行该命令的更改时发生。

        /// </summary>

        public event EventHandler CanExecuteChanged;

        /// <summary>

        /// 定义用于确定此命令是否可以在其当前状态下执行的方法。

        /// </summary>

        /// <param name="para"></param>

        /// <returns></returns>

        public bool CanExecute(object para)

        {

            if (para != null)

            {

                CanExecuteChanged(para, new EventArgs());

            }

            return true;

            //return false;

        }

        /// <summary>

        /// 定义在调用此命令时调用的方法。

        /// </summary>

        /// <param name="para"></param>

        public void Execute(object para)

        {

            MessageBox.Show("afdafd");



        }

 

    }

View Code

and in xaml

<UserControl.Resources>

        <dat:OpenChildWindowCommand x:Key="kk"></dat:OpenChildWindowCommand>

    </UserControl.Resources>

<Button Grid.Row="2" Margin="0,0,4,0" Height="40" Width="40" 

                 Command="{StaticResource kk}" />

and now you click this button you will see the messagebox.

In order to understand the ICommand

let's see it

  public interface ICommand

    {

        // Summary:

        //     Occurs when changes occur that affect whether the command should execute.

        event EventHandler CanExecuteChanged;



        // Summary:

        //     Defines the method that determines whether the command can execute in its

        //     current state.

        //

        // Parameters:

        //   parameter:

        //     Data used by the command. If the command does not require data to be passed,

        //     this object can be set to null.

        //

        // Returns:

        //     true if this command can be executed; otherwise, false.

        bool CanExecute(object parameter);

        //

        // Summary:

        //     Defines the method to be called when the command is invoked.

        //

        // Parameters:

        //   parameter:

        //     Data used by the command. If the command does not require data to be passed,

        //     this object can be set to null.

        void Execute(object parameter);

    }

View Code

Now it's clearly

if we want to set the method to the model first we need construct the class like below

 public class CommandHandler:ICommand

    {

        Action<object> _act;

        bool _canExecute;



        public CommandHandler(Action<object> act, bool canExecute)

        {

            _act = act;

            _canExecute = canExecute;

        }



        public bool CanExecute(object parameter)

        {

            return _canExecute;

        }



        public event EventHandler CanExecuteChanged;



        public void Execute(object parameter)

        {

            _act(parameter);

        }

    }

View Code

and now in our model class

 private ICommand _SaveCommand;

        public ICommand SaveCommand

        {

            get

            {

                return _SaveCommand = new CommandHandler(Save, _Execute);

            }

        }

        #endregion



        private void Save(object param)

        {

            ObservableCollection<Employee> newIM = new ObservableCollection<Employee>();

            foreach (Employee e in newIM)

            {

                string a = e.FirstName;

                string b = e.LastName;

            }

             or othething

        }

View Code