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http://stackoverflow.com/questions/1798513/wpf-toolkit-datepicker-month-year-only
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<DatePicker, DependencyPropertyChangedEventArgs>(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); } }
调用方式
<DatePicker Width="200" Height="30" local:DatePickerCalendar.IsMonthYear="True"/>
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<DatePicker>(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, string>(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<DatePicker, string>)parameter).Item2; var selectedDate = (DateTime?)value; return DateTimeToString(formatStr, selectedDate); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { var tupleParam = ((Tuple<DatePicker, string>)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; } } }
总的调用方法
<DatePicker conver:DatePickerCalendar.IsMonthYear="True" conver:DatePickerDateFormat.DateFormat="yyyy-MM" />
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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