MVVM开发模式MVVM Light Toolkit中使用事件和参数传递

Light中定义了类GalaSoft.MvvmLight.Command.RelayCommand

这个类继承了ICommand方法，实现了其中的方法，Action就是一个方法参数

// 摘要:

    //     A command whose sole purpose is to relay its functionality to other objects

    //     by invoking delegates. The default return value for the CanExecute method

    //     is 'true'. This class does not allow you to accept command parameters in

    //     the Execute and CanExecute callback methods.

    public class RelayCommand : ICommand

    {

        // 摘要:

        //     Initializes a new instance of the RelayCommand class that can always execute.



        public RelayCommand(Action execute);

        //

        // 摘要:

        //     Initializes a new instance of the RelayCommand class.



        public RelayCommand(Action execute, Func<bool> canExecute);



        // 摘要:

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

        public event EventHandler CanExecuteChanged;



        // 摘要:

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

        //     current state.



        [DebuggerStepThrough]

        public bool CanExecute(object parameter);

        //

        // 摘要:

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



        public void RaiseCanExecuteChanged();

    }

做一个简单的导航事件

从MainView导航到View1，

在View1的Viewmodel中定义这个事件属性

 public RelayCommand GotoView1
        {
            get;
            set;
        }

在构造函数中赋值给GotoView1

 GotoView1 = new RelayCommand(delegate {
                System.Windows.MessageBox.Show("Go to View1");
            });

//或者定义一个单独的方法  GotoView1 = new RelayCommand( ()=>GoToView1());

然后在MainPage.xaml中绑定事件

  <HyperlinkButton x:Name="View1" Grid.Row="1" Content="Go to View1" Command="{Binding GotoView1}" ></HyperlinkButton>

 

参数传递。

定义事件的时候很多情况下都需要传入参数，MVVM light也有这功能，而且 比较简单，方式如下：

//<string>这个就是GotoView1方法需要的参数，参数类型是string，当然可以根据需要变成其他类型，实体类型都可以

 public RelayCommand<string> GotoView1

        {

            get;

            set;

        }

  public void GoToView11(string msg)
  {
         System.Windows.MessageBox.Show(msg + "Go to View1");
  }

//对这个方法属性赋值,test只是形式参数，无任何意义，意思是把字符串类型的test传递给GotoView方法
GotoView1 = new RelayCommand<string>((test) => GoToView11(test));

页面上绑定这个方法的时候可以指定CommandParameter来指定Command的绑定方法的参数，如果类型是字符串，直接="字符串"就可以

如果是其他实体类型可以参考使用Binding语法CommandParameter="{Binding SelectedItem, ElementName=集合控件}"

            <HyperlinkButton x:Name="View1" Grid.Row="1" Content="Go to View1" Command="{Binding GotoView1}" CommandParameter="Hello" ></HyperlinkButton>