如何将 WPF 4.0 DatePicker 控件本地化

Question

当您在新的WPF 4.0 DatePicker控件中清除日期选择框时，它会显示“Select a date”。

是否有方法本地化文本？

- Eduardo Molteni

Answer 1

我借鉴了Matt的想法，并进行了一些扩展；我实现了一个Attached Behavior，它允许您通过XAML为每个DatePicker控件定义水印。以下是代码：

namespace DatePickerWatermark
{
    using System.Windows;
    using System.Windows.Controls;
    using System.Windows.Controls.Primitives;
    using System.Windows.Media;

    public static class DatePickerWatermarkBehaviour
    {
        public static readonly DependencyProperty WatermarkProperty =
            DependencyProperty.RegisterAttached(
                "Watermark",
                typeof(string),
                typeof(DatePickerWatermarkBehaviour),
                new UIPropertyMetadata(null, OnWatermarkChanged));

        public static string GetWatermark(Control control)
        {
            return (string)control.GetValue(WatermarkProperty);
        }

        public static void SetWatermark(Control control, string value)
        {
            control.SetValue(WatermarkProperty, value);
        }

        private static void OnWatermarkChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
        {
            var datePicker = dependencyObject as DatePicker;
            if (datePicker == null)
                return;

            if ((e.NewValue != null) && (e.OldValue == null))
                datePicker.Loaded += DatePickerLoaded;
            else if ((e.NewValue == null) && (e.OldValue != null))
                datePicker.Loaded -= DatePickerLoaded;
        }

        private static void DatePickerLoaded(object sender, RoutedEventArgs e)
        {
            var datePicker = sender as DatePicker;
            if (datePicker == null)
                return;

            var datePickerTextBox = GetFirstChildOfType<DatePickerTextBox>(datePicker);
            if (datePickerTextBox == null)
                return;

            var partWatermark = datePickerTextBox.Template.FindName("PART_Watermark", datePickerTextBox) as ContentControl;
            if (partWatermark == null)
                return;

            partWatermark.Content = GetWatermark(datePicker);
        }

        private static T GetFirstChildOfType<T>(DependencyObject dependencyObject) where T : DependencyObject
        {
            if (dependencyObject == null)
                return null;

            for (var i = 0; i < VisualTreeHelper.GetChildrenCount(dependencyObject); i++)
            {
                var child = VisualTreeHelper.GetChild(dependencyObject, i);
                var result = (child as T) ?? GetFirstChildOfType<T>(child);
                if (result != null)
                    return result;
            }

            return null;
        }
    }
}

以下是一些 XAML 示例：

<Window x:Class="DatePickerWatermark.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:b="clr-namespace:DatePickerWatermark" Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Grid.Resources>
            <Style TargetType="DatePicker">
                <Setter Property="Margin" Value="10,5"/>
            </Style>
            <Style x:Key="EnglishDatePicker" TargetType="DatePicker" BasedOn="{StaticResource {x:Type DatePicker}}">
                <Setter Property="b:DatePickerWatermarkBehaviour.Watermark" Value="Please select a date:"/>
            </Style>
        </Grid.Resources>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="200"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <DatePicker Grid.Row="0" b:DatePickerWatermarkBehaviour.Watermark=""/>
        <DatePicker Grid.Row="1" b:DatePickerWatermarkBehaviour.Watermark="Wählen Sie ein Datum"/>
        <DatePicker Grid.Row="2" b:DatePickerWatermarkBehaviour.Watermark="Sélectionner une date"/>
        <DatePicker Grid.Row="3" Style="{StaticResource EnglishDatePicker}"/>
        <DatePicker Grid.Row="4" Style="{StaticResource EnglishDatePicker}"/>
    </Grid>
</Window>

- Wayne Maurer

Answer 2

以下是不需要从DatePicker派生新控件的方法来完成此操作：

自定义WPF DatePicker的水印

- Matt Hamilton

Answer 3

很遗憾，设置水印文本有点棘手。

具体的操作可以参考这篇文章：更改日期选择器控件中的水印文本

- Oliver Vogel

---

WPF 方面有什么解决方案吗？ - papaiatis

Answer 4

Wayne，这很好用，但当DatePicker是DataGridColumnHeader的一部分时不起作用，有时当DatePicker在先隐藏后可见的控件上时也不起作用。Matt Hamilton的解决方案仅在onLoad时有效，当您更改selectedDate时，又会出现令人讨厌的“选择日期”水印。最简单的解决方案就是在自定义类中覆盖OnRender事件。如果您设置了watermark属性而不是需要覆盖onload事件的watermark内容，则完整的类在此处：

public class myDateTimePicker : DatePicker
{

    public string Watermark { get; set; }

    protected override void OnSelectedDateChanged(SelectionChangedEventArgs e)
    {
        base.OnSelectedDateChanged(e);
        //SetWatermark();
    }

    protected override void OnRender(System.Windows.Media.DrawingContext drawingContext)
    {
        base.OnRender(drawingContext);
        SetWatermark();
    }

    private void SetWatermark()
    {
        FieldInfo fiTextBox = typeof(DatePicker).GetField("_textBox", BindingFlags.Instance | BindingFlags.NonPublic);
        if (fiTextBox != null)
        {
            DatePickerTextBox dateTextBox = (DatePickerTextBox)fiTextBox.GetValue(this);
            if (dateTextBox != null)
            {
                if (string.IsNullOrWhiteSpace(this.Watermark))
                {
                    this.Watermark = "Custom watermark";
                }

                // if you set property this way then you need to override OnSelectedDateChanged event
                //PropertyInfo piWatermark = typeof(DatePickerTextBox).GetProperty("Watermark", BindingFlags.Instance | BindingFlags.NonPublic);
                //if (piWatermark != null)
                //{
                //    piWatermark.SetValue(dateTextBox, this.Watermark, null);
                //}

                var partWatermark = dateTextBox.Template.FindName("PART_Watermark", dateTextBox) as ContentControl;
                if (partWatermark != null)
                {
                    partWatermark.Foreground = new SolidColorBrush(Colors.Gray);
                    partWatermark.Content = this.Watermark;
                }
            }
        }
    }

}

- Mario Rancic