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我派生了 DatePicker 类以支持额外的 DateMode 属性，该属性将允许用户仅按照 DateMode（日、月、年）使用控件。因此，如果 DateMode 设置为 Year，则控件将无法进一步向下钻取以查看一年中的月份，然后再进一步查看月份中的几天。控制工作良好，但有一个问题。虽然我已经在 DatePicker 模板中的“PART_TextBox”控件上应用了字符串格式，这将根据 DateMode 更改格式，但一旦 DatePicker 控件失去焦点，格式就会丢失。以下是我派生的 DatePicker 控件代码：

public class MyDatePicker : DatePicker
{
    public string DateMode
    {
        get { return (string)GetValue(DateModeProperty); }
        set { SetValue(DateModeProperty, value); }
    }

    // Using a DependencyProperty as the backing store for DateMode.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty DateModeProperty =
        DependencyProperty.Register("DateMode", typeof(string), typeof(MyDatePicker), new UIPropertyMetadata("Day"));

    protected override void OnCalendarOpened(RoutedEventArgs e)
    {
        var popup = this.Template.FindName("PART_Popup", this) as Popup;
        var tb = this.Template.FindName("PART_TextBox", this) as TextBox;

        if (popup != null && popup.Child is System.Windows.Controls.Calendar)
        {
            if (DateMode == "Year")
                ((System.Windows.Controls.Calendar)popup.Child).DisplayMode = CalendarMode.Decade;
            else if (DateMode == "Month")
                ((System.Windows.Controls.Calendar)popup.Child).DisplayMode = CalendarMode.Year;
            else if (DateMode == "Day")
                ((System.Windows.Controls.Calendar)popup.Child).DisplayMode = CalendarMode.Month;
        }
        ((System.Windows.Controls.Calendar)popup.Child).DisplayModeChanged += new EventHandler<CalendarModeChangedEventArgs>(DatePickerCo_DisplayModeChanged);
    }

    protected override void OnCalendarClosed(RoutedEventArgs e)
    {
        base.OnCalendarClosed(e);
        IsDropDownOpen = false;
        var popup = this.Template.FindName("PART_Popup", this) as Popup;
        ((System.Windows.Controls.Calendar)popup.Child).DisplayModeChanged -= new EventHandler<CalendarModeChangedEventArgs>(DatePickerCo_DisplayModeChanged);
    }

    private void DatePickerCo_DisplayModeChanged(object sender, CalendarModeChangedEventArgs e)
    {
        var popup = this.Template.FindName("PART_Popup", this) as Popup;
        var tb = this.Template.FindName("PART_TextBox", this) as TextBox;

        if (popup != null && popup.Child is System.Windows.Controls.Calendar)
        {
            var _calendar = popup.Child as System.Windows.Controls.Calendar;

            if (DateMode == "Month" && _calendar.DisplayMode == CalendarMode.Month)
            {
                if (IsDropDownOpen)
                {
                    this.SelectedDate = _calendar.DisplayDate;
                    this.IsDropDownOpen = false;
                    _calendar.DisplayMode = CalendarMode.Year;
                }
                tb.Text = this.SelectedDate.Value.ToString("MMM yyyy");
            }
            else if (DateMode == "Year" && _calendar.DisplayMode == CalendarMode.Year)
            {
                if (IsDropDownOpen)
                {
                    this.SelectedDate = _calendar.DisplayDate;
                    this.IsDropDownOpen = false;
                    _calendar.DisplayMode = CalendarMode.Decade;
                }
                tb.Text = this.SelectedDate.Value.ToString("yyyy");
            }
        }
    }
 }
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1 回答 1

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我认为您可能会干扰基类。我不确定确切的设置，但我认为PART_TextBox有一个由 设置的绑定，DatePicker并且可能正在更新 LostFocus 并循环返回以清除Text您直接设置的值。您可以尝试使用BindingOperations.GetBinding来访问绑定Text并修改它的 StringFormat 而不是Text直接设置。

于 2013-02-07T21:11:47.467 回答