问题
i need datepicker in window store app , windows 8, but i am not able to find any control, so i used this :
jasonmitchell / WinRT-XAML-DatePicker
https://github.com/jasonmitchell/WinRT-XAML-DatePicker/blob/master/Samples/WinRTDatePicker.Samples.sln
but my problem is , by default it shows today date, that i don't want, i don't want to show any date, if user did not apply any date
if anybody have idea to working with date-picker in windows metro application, that will be great,
i know windows 8.1 have that control but i cannot moved to windows 8.1 now!
code example :
<WinRTDatePicker:DatePicker IsEnabled="True" x:Name="dtActualFinishDate" Width="370"/>
i want to set value if
if (Booking.ActualToDteTme.HasValue)
{
dtActualFinishDate.SelectedDate = Booking.ActualToDteTme.Value;
}
so if ActualToDteTme have any value, i want to apply otherwise, i need to keep datepicker is as blank,
for now it is show as currect date, and when i click on Update, it updated current date !! that's not right behaviour!!
Thanks
回答1:
I am giving you updated DatePicker & SelectedDateChangedEventArgs class. Use these classes instead from Github. I have added default "month", "date", "year" placeholder text. Default value will be null & if anyone selects placeholder text then also it will be null.
using System;
using System.Collections.ObjectModel;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Data;
namespace WinRTDatePicker
{
[TemplatePart(Name = "_DayOptions", Type = typeof(ComboBox))]
[TemplatePart(Name = "_MonthOptions", Type = typeof(ComboBox))]
[TemplatePart(Name = "_YearOptions", Type = typeof(ComboBox))]
public sealed class DatePicker : Control
{
public static readonly DependencyProperty SelectedDateProperty = DependencyProperty.Register("SelectedDate", typeof(DateTime?), typeof(DatePicker), new PropertyMetadata(default(DateTime?), SelectedDateChangedCallback));
public static readonly DependencyProperty DayOptionFormatProperty = DependencyProperty.Register("DayOptionFormat", typeof(string), typeof(DatePicker), new PropertyMetadata(default(string)));
public static readonly DependencyProperty MonthOptionFormatProperty = DependencyProperty.Register("MonthOptionFormat", typeof(string), typeof(DatePicker), new PropertyMetadata(default(string)));
public event EventHandler<SelectedDateChangedEventArgs> SelectedDateChanged;
private readonly ObservableCollection<string> daysInRange = new ObservableCollection<string>();
private readonly ObservableCollection<string> monthsInRange = new ObservableCollection<string>();
private readonly ObservableCollection<string> yearsInRange = new ObservableCollection<string>();
public DatePicker()
{
DefaultStyleKey = typeof(DatePicker);
//SelectedDate = DateTime.Today;
DayOptionFormat = "dd dddd";
MonthOptionFormat = "MMMM";
}
protected override void OnApplyTemplate()
{
base.OnApplyTemplate();
monthsInRange.Clear();
monthsInRange.Add("Month");
for (int i = 1; i <= 12; i++)
{
DateTime monthStart = new DateTime(DateTime.Now.Year, i, 1);
monthsInRange.Add(monthStart.ToString(MonthOptionFormat));
}
CreateBindings();
SetSelectedDate(SelectedDate);
DayOptions.SelectionChanged += DayOptionsOnSelectionChanged;
MonthOptions.SelectionChanged += MonthOptionsOnSelectionChanged;
YearOptions.SelectionChanged += YearOptionsOnSelectionChanged;
}
private void SetSelectedDate(DateTime? newSelectedDate)
{
if (DayOptions != null && MonthOptions != null && YearOptions != null)
{
var TempNewSelectedDate = newSelectedDate;
if (newSelectedDate == null)
{
newSelectedDate = DateTime.Today;
}
daysInRange.Clear();
yearsInRange.Clear();
daysInRange.Add("Date");
for (int i = 1; i <= DateTime.DaysInMonth(newSelectedDate.Value.Year, newSelectedDate.Value.Month); i++)
{
DateTime date = new DateTime(newSelectedDate.Value.Year, newSelectedDate.Value.Month, i);
daysInRange.Add(date.ToString(DayOptionFormat));
}
int minYear = newSelectedDate.Value.Year - 10;
int maxYear = newSelectedDate.Value.Year + 10;
yearsInRange.Add("Year");
for (int i = minYear; i <= maxYear; i++)
{
yearsInRange.Add(i.ToString());
}
if (TempNewSelectedDate != null)
{
DayOptions.SelectedIndex = newSelectedDate.Value.Day;
MonthOptions.SelectedIndex = newSelectedDate.Value.Month;
YearOptions.SelectedItem = newSelectedDate.Value.Year.ToString();
}
else
{
DayOptions.SelectedIndex = 0;
MonthOptions.SelectedIndex = 0;
YearOptions.SelectedIndex = 0;
}
}
}
private void CreateBindings()
{
Binding dayOptionsBinding = new Binding { Source = daysInRange, Mode = BindingMode.OneWay };
DayOptions.SetBinding(ItemsControl.ItemsSourceProperty, dayOptionsBinding);
Binding monthOptionsBinding = new Binding { Source = monthsInRange, Mode = BindingMode.OneWay };
MonthOptions.SetBinding(ItemsControl.ItemsSourceProperty, monthOptionsBinding);
Binding yearOptionsBinding = new Binding { Source = yearsInRange, Mode = BindingMode.OneWay };
YearOptions.SetBinding(ItemsControl.ItemsSourceProperty, yearOptionsBinding);
}
private void UpdateSelectedDateFromInputs()
{
if (YearOptions.SelectedIndex > 0 && MonthOptions.SelectedIndex > 0 && DayOptions.SelectedIndex > 0)
{
int year = int.Parse(YearOptions.SelectedValue.ToString());
int month = MonthOptions.SelectedIndex;
int day = DayOptions.SelectedIndex;
int maxDaysInMonth = DateTime.DaysInMonth(year, month);
if (day > maxDaysInMonth)
{
day = maxDaysInMonth;
DayOptions.SelectedIndex = maxDaysInMonth - 1;
}
if (month == 0)
month = 1;
if (day == 0)
day = 1;
SelectedDate = new DateTime(year, month, day);
}
else if (YearOptions.SelectedIndex == 0 && MonthOptions.SelectedIndex == 0 && DayOptions.SelectedIndex == 0)
{
SelectedDate = null;
}
}
private void UpdateDayOptions()
{
if (SelectedDate != null)
{
int selectedDayIndex = DayOptions.SelectedIndex;
int month = MonthOptions.SelectedIndex;
if (month != 0)
{
daysInRange.Clear();
daysInRange.Add("Date");
for (int i = 1; i <= DateTime.DaysInMonth(SelectedDate.Value.Year, month); i++)
{
DateTime date = new DateTime(SelectedDate.Value.Year, month, i);
daysInRange.Add(date.ToString(DayOptionFormat));
}
DayOptions.SelectedIndex = selectedDayIndex;
}
}
}
private void DayOptionsOnSelectionChanged(object sender, SelectionChangedEventArgs selectionChangedEventArgs)
{
UpdateSelectedDateFromInputs();
}
private void MonthOptionsOnSelectionChanged(object sender, SelectionChangedEventArgs selectionChangedEventArgs)
{
UpdateSelectedDateFromInputs();
UpdateDayOptions();
}
private void YearOptionsOnSelectionChanged(object sender, SelectionChangedEventArgs selectionChangedEventArgs)
{
UpdateSelectedDateFromInputs();
UpdateDayOptions();
}
private static void SelectedDateChangedCallback(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
DateTime oldValue = args.OldValue != null ? (DateTime)args.OldValue : DateTime.Today.AddDays(-1);
DateTime? newValue = (DateTime?)args.NewValue;
if (newValue != oldValue)
{
DatePicker datePicker = (DatePicker)obj;
datePicker.SetSelectedDate(newValue);
if (datePicker.SelectedDateChanged != null)
datePicker.SelectedDateChanged(datePicker, new SelectedDateChangedEventArgs(newValue));
}
}
public DateTime? SelectedDate
{
get { return (DateTime?)GetValue(SelectedDateProperty); }
set { SetValue(SelectedDateProperty, value); }
}
public string DayOptionFormat
{
get { return (string)GetValue(DayOptionFormatProperty); }
set { SetValue(DayOptionFormatProperty, value); }
}
public string MonthOptionFormat
{
get { return (string)GetValue(MonthOptionFormatProperty); }
set { SetValue(MonthOptionFormatProperty, value); }
}
private ComboBox DayOptions
{
get { return (ComboBox)GetTemplateChild("_DayOptions"); }
}
private ComboBox MonthOptions
{
get { return (ComboBox)GetTemplateChild("_MonthOptions"); }
}
private ComboBox YearOptions
{
get { return (ComboBox)GetTemplateChild("_YearOptions"); }
}
}
}
using System;
namespace WinRTDatePicker
{
public class SelectedDateChangedEventArgs : EventArgs
{
private readonly DateTime? newDate;
public SelectedDateChangedEventArgs(DateTime? newDate)
{
this.newDate = newDate;
}
public DateTime? NewDate
{
get { return newDate; }
}
}
}
回答2:
For the binding to work you should change SelectedDateProperty to
public static readonly DependencyProperty SelectedDateProperty =
DependencyProperty.Register("SelectedDate",
typeof(object),
typeof(NullableDatePicker),
new PropertyMetadata(null, SelectedDateChangedCallback));
to avoid the error:
Error: Converter failed to convert value of type 'System.DateTime, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' to type 'Nullable`1';
来源：https://stackoverflow.com/questions/20535604/windows-store-app-date-picker-null-date