c# - 如何在属性更新后调用方法

Question

我有一个绑定(bind)到 viewmodel.SelectedDate 的 DatePicker 控件。我没有使用 propfull，而是使用 CTK [ObservableProperty]。当我选择一个新日期时，我想调用另一个函数，该函数根据该新日期获取新的数据集。还有其他注释吗？

    /// Set by the Date Control on the form
    [ObservableProperty]
    //[AlsoCallThisFunction(DisplayBookings)]
    public DateTime bookingDate;

    ///I want to call this for a fresh dataset
    ///after the bookingDate is set
    void DisplayBookings()
    {
        GoToDatabaseAndGetNewRecordset(bookingDate);
    }

旧的做法:

    //private DateTime bookingDate;

    //public DateTime BookingDate
    //{
    //    get { return bookingDate; }
    //    set { 
    //        bookingDate = value;
    //        DisplayBookings();

    //    }
    //}

Answer 1

您可以重写 OnPropertyChanging 和 OnPropertyChanged 事件，并在那里调用您的方法。

请记住，如果您将绑定(bind)设置为 UpdateSourceTrigger=PropertyChanged，则某些更改可能仍在进行。

protected override void OnPropertyChanged(PropertyChangedEventArgs e)
{
    base.OnPropertyChanged(e);

    if (e.PropertyName == nameof(BookingDate))
    {
        DisplayBookings();
    }
}

更新

起始于 v8.0.0 Preview 3您可以使用部分属性更改方法。

引自博客:

When using [ObservableProperty] to generate observable properties, the MVVM Toolkit will now also generate two partial methods with no implementations: On<PROPERTY_NAME>Changing and On<PROPERTY_NAME>Changed. These methods can be used to inject additional logic when a property is changed, without the need to fallback to using a manual property. Note that because these two methods are partial, void-returning and with no definition, the C# compiler will completely remove them if they are not implemented, meaning that when not used they will simply vanish and add no overhead to the application

然后你可以将其重写为:

[ObservableProperty]
public DateTime bookingDate;

partial void OnBookingDateChanged(DateTime bookingDate)
{
    DisplayBookings();
}