Question

我需要将WPF DatePicker中DatePickerTextBox的字符串格式更改为“mm / dd / yyyy”的“dd / MM / YYYY”。我想允许用户手动添加日期。当我以这种格式键入TextBox时：“mm / dd / yyyy”DatePicker中的日期更改。但是当我输入这种格式时：“dd / MM / yyy”我收到了一个错误。我试过：StringFormat ='dd / MM / yyyy'，但它没有帮助：

Answer 1

您在ConvertBack方法上获得了例外：

Exception thrown: 'System.FormatException' in mscorlib.dll
Exception thrown: 'System.Reflection.TargetInvocationException' in mscorlib.dll
Exception thrown: 'System.FormatException' in mscorlib.dll
System.Windows.Data Error: 7 : ConvertBack cannot convert value '14/09/2016' (type 'String'). BindingExpression:Path=SelectedDate; DataItem='DatePicker' (Name='DateGviya'); target element is 'TextBox' (Name='PART_TextBox'); target property is 'Text' (type 'String') FormatException:'System.FormatException: String was not recognized as a valid DateTime.
   at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
   at System.Convert.ToDateTime(String value, IFormatProvider provider)
   at System.String.System.IConvertible.ToDateTime(IFormatProvider provider)
   at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
   at MS.Internal.Data.SystemConvertConverter.ConvertBack(Object o, Type type, Object parameter, CultureInfo culture)
   at System.Windows.Data.BindingExpression.ConvertBackHelper(IValueConverter converter, Object value, Type sourceType, Object parameter, CultureInfo culture)'

因此，提供自定义转换器可以解决问题：

public class MyCustomDateConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value != null)
            return ((DateTime)value).ToString("dd/MM/yyyy hh:mm:ss tt", culture);

        return null;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return DateTime.ParseExact((string)value, "dd/MM/yyyy hh:mm:ss tt", culture);
    }
}

<强> XAML：

<Window x:Class="WpfApplication293.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:WpfApplication293"
    mc:Ignorable="d"
    Title="Window1" Height="350" Width="350">

<Window.Resources>

    <local:MyCustomDateConverter x:Key="Converter1" />

</Window.Resources>

<Window.DataContext>
    <local:MyViewModel/>
</Window.DataContext>

<Grid>
    <DatePicker x:Name="DateGviya" SelectedDate="{Binding CurrentDate}"  HorizontalAlignment="Center" VerticalAlignment="Top">
        <DatePicker.Resources>
            <Style TargetType="{x:Type DatePickerTextBox}">
                <Setter Property="Control.Template">
                    <Setter.Value>
                        <ControlTemplate>
                            <TextBox x:Name="PART_TextBox" Text="{Binding Path=SelectedDate, StringFormat='dd/MM/yyyy hh:mm:ss tt', RelativeSource={RelativeSource AncestorType={x:Type DatePicker}}, Converter={StaticResource Converter1}}" />
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </DatePicker.Resources>
    </DatePicker>
</Grid>

自定义WPF DatePicker Mask

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