Changing the string format of the WPF DatePicker

Question

I need to change the string format of the DatePickerTextBox in the WPF Toolkit DatePicker, to use hyphens instead of slashes for the seperators.

Is there a way to override this default culture or the display string format?

01-01-2010

Answer 1

Unfortunately, if you are talking about XAML, you are stuck with setting SelectedDateFormat to "Long" or "Short".

If you downloaded the source of the Toolkit along with the binaries, you can see how it is defined. Here are some of the highlights of that code:

DatePicker.cs

#region SelectedDateFormat

/// <summary>
/// Gets or sets the format that is used to display the selected date.
/// </summary>
public DatePickerFormat SelectedDateFormat
{
    get { return (DatePickerFormat)GetValue(SelectedDateFormatProperty); }
    set { SetValue(SelectedDateFormatProperty, value); }
}

/// <summary>
/// Identifies the SelectedDateFormat dependency property.
/// </summary>
public static readonly DependencyProperty SelectedDateFormatProperty =
    DependencyProperty.Register(
    "SelectedDateFormat",
    typeof(DatePickerFormat),
    typeof(DatePicker),
    new FrameworkPropertyMetadata(OnSelectedDateFormatChanged),
    IsValidSelectedDateFormat);

/// <summary>
/// SelectedDateFormatProperty property changed handler.
/// </summary>
/// <param name="d">DatePicker that changed its SelectedDateFormat.</param>
/// <param name="e">DependencyPropertyChangedEventArgs.</param>
private static void OnSelectedDateFormatChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    DatePicker dp = d as DatePicker;
    Debug.Assert(dp != null);

    if (dp._textBox != null)
    {
        // Update DatePickerTextBox.Text
        if (string.IsNullOrEmpty(dp._textBox.Text))
        {
            dp.SetWaterMarkText();
        }
        else
        {
            DateTime? date = dp.ParseText(dp._textBox.Text);

            if (date != null)
            {
                dp.SetTextInternal(dp.DateTimeToString((DateTime)date));
            }
        }
    }
}



#endregion SelectedDateFormat

private static bool IsValidSelectedDateFormat(object value)
{
    DatePickerFormat format = (DatePickerFormat)value;

    return format == DatePickerFormat.Long
        || format == DatePickerFormat.Short;
}

private string DateTimeToString(DateTime d)
{
    DateTimeFormatInfo dtfi = DateTimeHelper.GetCurrentDateFormat();

    switch (this.SelectedDateFormat)
    {
        case DatePickerFormat.Short:
            {
                return string.Format(CultureInfo.CurrentCulture, d.ToString(dtfi.ShortDatePattern, dtfi));
            }

        case DatePickerFormat.Long:
            {
                return string.Format(CultureInfo.CurrentCulture, d.ToString(dtfi.LongDatePattern, dtfi));
            }
    }      

    return null;
}

DatePickerFormat.cs

public enum DatePickerFormat
{
    /// <summary>
    /// Specifies that the date should be displayed 
    /// using unabbreviated days of the week and month names.
    /// </summary>
    Long = 0,

    /// <summary>
    /// Specifies that the date should be displayed 
    ///using abbreviated days of the week and month names.
    /// </summary>
    Short = 1
}

Answer 2

It appears, as per Wonko's answer, that you cannot specify the Date format in Xaml format or by inheriting from the DatePicker.

I have put the following code into my View's constructor which overrides the ShortDateFormat for the current thread:

CultureInfo ci = CultureInfo.CreateSpecificCulture(CultureInfo.CurrentCulture.Name);
ci.DateTimeFormat.ShortDatePattern = "dd-MM-yyyy";
Thread.CurrentThread.CurrentCulture = ci;