Question

您好我正在学习Josh Smith的Wpf应用并尝试了解MVVM模式。您可以从here

下载该应用

我的问题很简单，应用程序在MainView上定义了菜单项，这些菜单项绑定到MainWindow视图模型。我需要单击菜单选项以触发CustomerViewModel中的复选框。到目前为止，这就是我所做的，我将menuitem click命令连接到MainWindowViewModel中的方法，然后此方法引发一个名为OptionsMenuItemClicked的事件。然后我在CustomerViewModel上实现了一个监听器，这个监听器会调用一个方法，该方法应该对复选框进行检查。引发了该事件，但该方法未触发。谁能请帮忙。这是我想要实现的屏幕截图：

enter image description here

以下是我所做的代码，我希望有人可以指出我正确的方向

XAML

 <MenuItem Header="Options">
            <MenuItem Header="Check"
                      Command="{Binding Path= CheckCommand}"/>
                </MenuItem>

MainWindowViewModel

 public event EventHandler CheckMenuItemClicked = delegate { };


    private RelayCommand _checkCommand;

    public ICommand CheckCommand
    {
        get
        {
            if(_checkCommand == null)
            {
                _checkCommand = new RelayCommand(param=>this.RaiseEventForCustomerViewModel());
            }
            return _checkCommand;
        }
    }

    private void RaiseEventForCustomerViewModel()
    {
        EventHandler handler = this.CheckMenuItemClicked;
        if (handler != null)
        {
            handler(this, EventArgs.Empty);
        }
    }

CustomerViewModel

    public CustomerViewModel(Customer customer, CustomerRepository customerRepository)
    {
        if (customer == null)
            throw new ArgumentNullException("customer");

        if (customerRepository == null)
            throw new ArgumentNullException("customerRepository");

        _customer = customer;
        _customerRepository = customerRepository;
        _customerType = Strings.CustomerViewModel_CustomerTypeOption_NotSpecified;
        MainWindowViewModel vm = new MainWindowViewModel(null);
        vm.CheckMenuItemClicked += vm_CheckMenuItemClicked;
    }

    void vm_CheckMenuItemClicked(object sender, EventArgs e)
    {
        //logic to check the check box
    }

Answer 1

问题是：

   MainWindowViewModel vm = new MainWindowViewModel(null);
   vm.CheckMenuItemClicked += vm_CheckMenuItemClicked;

您只是附加到MainWindowViewModel的错误实例。 此事件未触发此事件，因为它与窗口的DataContext不同。

void someFunctionInsideMainWindowViewModel()
{
    CustomerViewModel customerVm = new CustomerViewModel(...);
    this.OptionsMenuItemClicked += (sender, e)=>
    {
        //logic to check the check box
        //you have access to customerVm from here
    };
}

Wpf MVVM Josh Smith App以编程方式检查Customer View Viewmodel中的复选框

1 个答案: