WPF ICommand

First, the purpose

Code decrease the degree of coupling (coupling code UI layer and low layer BLL), the better the code behind the UI layer is transferred to the BLL layer, and the view to better business logic

Second, use

1. Create a RelayCommand, inherited ICommand interface

    public class RelayCommand : ICommand
    {
        #region Fields
        private readonly Func<Object, Boolean> _canExecute;
        private readonly Action<Object> _execute;
        #endregion

        #region Constructors
        public RelayCommand(Action<Object> execute) : this(execute, null)
        {
        }

        public RelayCommand(Action<Object> execute, Func<Object, Boolean> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException("execute");

            _execute = execute;
            _canExecute = canExecute;
        }
        #endregion

        #region ICommand Members
        public event EventHandler CanExecuteChanged
        {
            add
            {
                if (_canExecute != null)
                    CommandManager.RequerySuggested += value;
            }
            remove
            {
                if (_canExecute != null)
                    CommandManager.RequerySuggested -= value;
            }
        }

        [DebuggerStepThrough]
        public Boolean CanExecute(Object parameter)
        {
            return _canExecute == null ? true : _canExecute(parameter);
        }

        public void Execute(Object parameter)
        {
            _execute(parameter);
        }
        #endregion
    }

2. Create a ViewModel class, create an object property RelayCommand

(1) using a lambda expression

public class ViewModelTest
    {
        public ICommand ShowMessage
        {
            get
            {
                return new RelayCommand(new Action<Object>(t =>
                {
                    if (t == null)
                        MessageBox.Show("not have param");
                    else
                        MessageBox.Show(t.ToString());
                }));
            }
        }
    }

(2) using the function

    public class ViewModelTest
    {

        private void UpdateNameExecute(Object parameter)
        {
            MessageBox.Show("haha");
        }

        private bool CanUpdateNameExecute(Object parameter)
        {
            return true;
        }

        public ICommand ShowMessage
        {
            get
            {
                return new RelayCommand(UpdateNameExecute, CanUpdateNameExecute);
            }
        }
    }

3. Background class interface, the contents of the context object is assigned ViewModel

 DataContext = new ViewModelTest();

4. binding interface named

(1) without parameters

<Button Width="60" Height="30" Command="{Binding ShowMessage}"/>

(2) with parameters

 <Button Width="60" Height="30" Command="{Binding ShowMessage}" CommandParameter="have param"/>

 

 

reference:

https://www.cnblogs.com/weiweiboqi/p/4682136.html