WPF DatePicker只显示年和月修改：可以只显示年-白红宇

WPF DatePicker只显示年和月修改：可以只显示年

阅读量：5144 次

发布时间：2019-06-13

本文共 10541 字，大约阅读时间需要 35 分钟。

最近的项目，查询时只需要年和月，不需要日，因此需要对原有的DatePicker进行修改，查询了网上的内容，最终从一篇帖子里看到了添加附加属性的方法，地址是

原文是用了两个类，其中一个是为了让DatePicker下的Calendar只显示年月，不显示日，另一个类是为了让DatePicker格式化为yyyy-MM格式，但是从文章中可以看出，有人提出了，用格式化类进行格式化时，DatePicker控件会闪动一下，当然不影响使用。如果不想使用文章中提到的类进行格式化，也可以用我上一篇文章中的方法进行格式化，不会出现闪动的情况。

只显示年月的类（2016-12-20修改，可以只显示年）

public class DatePickerCalendar    {        public static bool GetIsYear(DependencyObject obj)        {            return (bool)obj.GetValue(IsYearProperty);        }        public static void SetIsYear(DependencyObject obj, bool value)        {            obj.SetValue(IsYearProperty, value);        }        // Using a DependencyProperty as the backing store for IsYear.  This enables animation, styling, binding, etc...        public static readonly DependencyProperty IsYearProperty =            DependencyProperty.RegisterAttached("IsYear", typeof(bool), typeof(DatePickerCalendar), new PropertyMetadata(false, new PropertyChangedCallback(OnIsMonthYearChanged)));        public static readonly DependencyProperty IsMonthYearProperty =        DependencyProperty.RegisterAttached("IsMonthYear", typeof(bool), typeof(DatePickerCalendar),                                            new PropertyMetadata(OnIsMonthYearChanged));        public static bool GetIsMonthYear(DependencyObject dobj)        {            return (bool)dobj.GetValue(IsMonthYearProperty);        }        public static void SetIsMonthYear(DependencyObject dobj, bool value)        {            dobj.SetValue(IsMonthYearProperty, value);        }        private static void OnIsMonthYearChanged(DependencyObject dobj, DependencyPropertyChangedEventArgs e)        {            var datePicker = (DatePicker)dobj;            Application.Current.Dispatcher                .BeginInvoke(DispatcherPriority.Loaded,                             new Action
      
       (SetCalendarEventHandlers),                             datePicker, e);        }        private static void SetCalendarEventHandlers(DatePicker datePicker, DependencyPropertyChangedEventArgs e)        {            if (e.NewValue == e.OldValue)                return;            if ((bool)e.NewValue)            {                datePicker.CalendarOpened += DatePickerOnCalendarOpened;                datePicker.CalendarClosed += DatePickerOnCalendarClosed;            }            else            {                datePicker.CalendarOpened -= DatePickerOnCalendarOpened;                datePicker.CalendarClosed -= DatePickerOnCalendarClosed;            }        }        private static void DatePickerOnCalendarOpened(object sender, RoutedEventArgs routedEventArgs)        {            var calendar = GetDatePickerCalendar(sender);            if (GetIsYear(sender as DatePicker))            {                calendar.DisplayMode = CalendarMode.Decade;            }            else            {                calendar.DisplayMode = CalendarMode.Year;            }            calendar.DisplayModeChanged += CalendarOnDisplayModeChanged;        }        private static void DatePickerOnCalendarClosed(object sender, RoutedEventArgs routedEventArgs)        {            var datePicker = (DatePicker)sender;            var calendar = GetDatePickerCalendar(sender);            datePicker.SelectedDate = calendar.SelectedDate;            calendar.DisplayModeChanged -= CalendarOnDisplayModeChanged;        }        private static void CalendarOnDisplayModeChanged(object sender, CalendarModeChangedEventArgs e)        {            var calendar = (Calendar)sender;            var datePicker = GetCalendarsDatePicker(calendar);            bool mode = (GetIsYear(datePicker) && calendar.DisplayMode != CalendarMode.Year) || (GetIsMonthYear(datePicker) && calendar.DisplayMode != CalendarMode.Month);            if (mode)                return;            calendar.SelectedDate = GetSelectedCalendarDate(calendar.DisplayDate);            datePicker.IsDropDownOpen = false;        }        private static Calendar GetDatePickerCalendar(object sender)        {            var datePicker = (DatePicker)sender;            var popup = (Popup)datePicker.Template.FindName("PART_Popup", datePicker);            return ((Calendar)popup.Child);        }        private static DatePicker GetCalendarsDatePicker(FrameworkElement child)        {            var parent = (FrameworkElement)child.Parent;            if (parent.Name == "PART_Root")                return (DatePicker)parent.TemplatedParent;            return GetCalendarsDatePicker(parent);        }        private static DateTime? GetSelectedCalendarDate(DateTime? selectedDate)        {            if (!selectedDate.HasValue)                return null;            return new DateTime(selectedDate.Value.Year, selectedDate.Value.Month, 1);        }    }

DatePickerCalendar

调用方式

展示效果

从图上就能看到左右不一样，左侧的是添加附加属性的，点击以后直接显示月，后侧没用的则显示到日，虽然都格式化为了yyyy-MM，但是Calendar如果显示到日的话，用户体验不好。

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2015年8月4日记：

今天在项目中发现一个问题，就是采用我上一篇帖子中的三句话进行DatePicker时间的格式化显示，但是由于用的是Thread，所以是在线程里进行格式化的，因此，影响到了同事做的其他模块，因为大部分都是格式化为yyyy-MM-dd，但是由于我的一个页面是格式化为了yyyy-MM，而其中的一个同事并没有在他的构造函数里使用三句格式化他的DatePicker，从而导致他其他的时间计算出现问题，因此在保证原有功能不变的情况下，需要显示yyyy-MM，就需要用到原帖子中的另一个类。

DatePickerDateFormat

public class DatePickerDateFormat    {        public static readonly DependencyProperty DateFormatProperty =DependencyProperty.RegisterAttached("DateFormat", typeof(string), typeof(DatePickerDateFormat),                                    new PropertyMetadata(OnDateFormatChanged));        public static string GetDateFormat(DependencyObject dobj)        {            return (string)dobj.GetValue(DateFormatProperty);        }        public static void SetDateFormat(DependencyObject dobj, string value)        {            dobj.SetValue(DateFormatProperty, value);        }        private static void OnDateFormatChanged(DependencyObject dobj, DependencyPropertyChangedEventArgs e)        {            var datePicker = (DatePicker)dobj;            Application.Current.Dispatcher.BeginInvoke(                DispatcherPriority.Loaded, new Action
      
       (ApplyDateFormat), datePicker);        }        private static void ApplyDateFormat(DatePicker datePicker)        {            var binding = new Binding("SelectedDate")            {                RelativeSource = new RelativeSource { AncestorType = typeof(DatePicker) },                Converter = new DatePickerDateTimeConverter(),                ConverterParameter = new Tuple
       
        (datePicker, GetDateFormat(datePicker))            };            var textBox = GetTemplateTextBox(datePicker);            textBox.SetBinding(TextBox.TextProperty, binding);            textBox.PreviewKeyDown -= TextBoxOnPreviewKeyDown;            textBox.PreviewKeyDown += TextBoxOnPreviewKeyDown;            datePicker.CalendarOpened -= DatePickerOnCalendarOpened;            datePicker.CalendarOpened += DatePickerOnCalendarOpened;        }        private static TextBox GetTemplateTextBox(Control control)        {            control.ApplyTemplate();            return (TextBox)control.Template.FindName("PART_TextBox", control);        }        private static void TextBoxOnPreviewKeyDown(object sender, KeyEventArgs e)        {            if (e.Key != Key.Return)                return;            /* DatePicker subscribes to its TextBox's KeyDown event to set its SelectedDate if Key.Return was             * pressed. When this happens its text will be the result of its internal date parsing until it             * loses focus or another date is selected. A workaround is to stop the KeyDown event bubbling up             * and handling setting the DatePicker.SelectedDate. */            e.Handled = true;            var textBox = (TextBox)sender;            var datePicker = (DatePicker)textBox.TemplatedParent;            var dateStr = textBox.Text;            var formatStr = GetDateFormat(datePicker);            datePicker.SelectedDate = DatePickerDateTimeConverter.StringToDateTime(datePicker, formatStr, dateStr);        }        private static void DatePickerOnCalendarOpened(object sender, RoutedEventArgs e)        {            /* When DatePicker's TextBox is not focused and its Calendar is opened by clicking its calendar button             * its text will be the result of its internal date parsing until its TextBox is focused and another             * date is selected. A workaround is to set this string when it is opened. */            var datePicker = (DatePicker)sender;            var textBox = GetTemplateTextBox(datePicker);            var formatStr = GetDateFormat(datePicker);            textBox.Text = DatePickerDateTimeConverter.DateTimeToString(formatStr, datePicker.SelectedDate);        }        private class DatePickerDateTimeConverter : IValueConverter        {            public object Convert(object value, Type targetType, object parameter, CultureInfo culture)            {                var formatStr = ((Tuple
        
         )parameter).Item2;                var selectedDate = (DateTime?)value;                return DateTimeToString(formatStr, selectedDate);            }            public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)            {                var tupleParam = ((Tuple
         
          )parameter);                var dateStr = (string)value;                return StringToDateTime(tupleParam.Item1, tupleParam.Item2, dateStr);            }            public static string DateTimeToString(string formatStr, DateTime? selectedDate)            {                return selectedDate.HasValue ? selectedDate.Value.ToString(formatStr) : null;            }            public static DateTime? StringToDateTime(DatePicker datePicker, string formatStr, string dateStr)            {                DateTime date;                var canParse = DateTime.TryParseExact(dateStr, formatStr, CultureInfo.CurrentCulture,                                                      DateTimeStyles.None, out date);                if (!canParse)                    canParse = DateTime.TryParse(dateStr, CultureInfo.CurrentCulture, DateTimeStyles.None, out date);                return canParse ? date : datePicker.SelectedDate;            }        }    }

DatePickerDateFormat

总的调用方法

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2016年12月20日

修改原来的代码，增加IsYear附加属性，用法和IsMonthYear一样，设置为True则只显示年份

转载于:https://www.cnblogs.com/ZXdeveloper/p/4665772.html

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