WPF PRISM 6 DelegateComand ObservesCanExecute

Question

提前致谢!

我应该如何在PRISM 6的DelegateCommand中使用ObservesCanExecute？

public partial class  UserAccountsViewModel: INotifyPropertyChanged
{
    public DelegateCommand InsertCommand { get; private set; }
    public DelegateCommand UpdateCommand { get; private set; }
    public DelegateCommand DeleteCommand { get; private set; }

    public UserAccount SelectedUserAccount
    {
        get;
        set
        {
            //notify property changed stuff
        }
    }

    public UserAccountsViewModel()
    {
        InitCommands();
    }

    private void InitCommands()
    {
        InsertCommand = new DelegateCommand(Insert, CanInsert);  
        UpdateCommand = new DelegateCommand(Update,CanUpdate).ObservesCanExecute(); // ???
        DeleteCommand = new DelegateCommand(Delete,CanDelete);
    }

    //----------------------------------------------------------

    private void Update()
    {
        //...
    }

    private bool CanUpdate()
    {
        return SelectedUserAccount != null;
    }

    //.....
}

不幸的是,我不熟悉c#中的表达式.另外,我认为这对其他人有帮助.

Answer 1

ObservesCanExecute()作品"大多喜欢"的canExecuteMethod参数DelegateCommand(Action executeMethod, Func<bool> canExecuteMethod).

但是,如果您有布尔属性而不是方法,则无需定义canExecuteMethodwith ObservesCanExecute.

在你的例子中,假设这CanUpdate不是一个方法,只是假设它是一个布尔属性.

然后,您可以更改代码ObservesCanExecute(() => CanUpdate)和DelegateCommand如果将只执行CanUpdate布尔属性的值为true(不需要定义一个方法).

ObservesCanExecute就像是属性上的"快捷方式",而不必定义方法并将其传递给构造函数的canExecuteMethod参数DelegateCommand.