Using C# Build a simple WPF app for picking a date and time. a calendar for date

ID: 3747195 • Letter: U

Question

Using C#

Build a simple WPF app for picking a date and time.

a calendar for date selection.

a textbox for time display
“Up” and “Down” buttons to adjust time. Hours, minutes and AM/PM should be incremented or decremented based on the cursor position. For example, you would want to be able to do a continuous adjustment on minutes when the cursor is placed in the minutes field
a “Select” botton that when clicked, should print a message (either in the MainWindow with a textbox, or a Message box) in the following format: “Your appointment is on Wednesday, March 2, 2018 at 9:15AM. It’s 18 days from today.”1. Use DateTime struct from .NET Class Library to handle date and time

2. Calendar is a built-in UI element that you can drag from the Toolbox and it’s ready to use. Use Calendar_SelectedDatesChanged event for date selection.

3. To parse time from textbox,

DateTime.Parse Method (String)
4. To adjust time with Up & Down button, DateTime.AddHours Method (Double)

Similarly for AddMinutes. AM/PM is simply a 12-hour changes

. 5. Adjustment of hours, minutes, AM/PM should be based on cursor position. It can be tricky to do the continuously adjustment on hrs/min/am/pm. The following property can be useful. TextBox.SelectionStart Property: Gets or sets a character index for the beginning of the current selection.

TextBox.CaretIndex Property: Gets or sets the insertion position index of the caret.

Explanation / Answer

Answer:

DateTimePicker.xaml

DateTimePicker.xaml.cs

using System;

using System.Globalization;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Input;

using System.Windows.Markup;

using System.Diagnostics;

using System.Windows.Media;

using System.Windows.Documents;

using System.Windows.Shapes;

namespace DTPicker

{

public partial class DateTimePicker : UserControl

{

private const int FormatLengthOfLast = 2;

private enum Direction : int

{

Previous = -1,

Next = 1

}

TextBoxUpDownAdorner _upDownButtons;

public DateTimePicker()

{

InitializeComponent();

CalDisplay.SelectedDatesChanged += CalDisplay_SelectedDatesChanged;

DateDisplay.PreviewMouseUp += DateDisplay_PreviewMouseUp;

DateDisplay.LostFocus += DateDisplay_LostFocus;

DateDisplay.PreviewKeyDown += DateTimePicker_PreviewKeyDown;

DateDisplay.TextChanged += new TextChangedEventHandler(DateDisplay_TextChanged);

this.Loaded += (s, e) =>

{

AdornerLayer adLayer = GetAdornerLayer(DateDisplay);

if (adLayer != null)

{

adLayer.Add(_upDownButtons = new TextBoxUpDownAdorner(DateDisplay));

_upDownButtons.Click += (textBox, direction) => { OnUpDown(direction); };

}

};

}

static AdornerLayer GetAdornerLayer(FrameworkElement subject)

{

AdornerLayer layer = null;

do {

if ((layer = AdornerLayer.GetAdornerLayer(subject)) != null)

break;

} while ((subject = subject.Parent as FrameworkElement) != null);

return layer;

}

#region "Properties"

public DateTime SelectedDate

{

get { return (DateTime)GetValue(SelectedDateProperty); }

set { SetValue(SelectedDateProperty, value); }

}

public string DateFormat

{

get { return Convert.ToString(GetValue(DateFormatProperty)); }

set { SetValue(DateFormatProperty, value); }

}

public bool ShowCalendarButton

{

get { return PopUpCalendarButton.Visibility == Visibility.Visible; }

set { PopUpCalendarButton.Visibility = (value ? Visibility.Visible : Visibility.Collapsed); }

}

public string _inputDateFormat;

public string InputDateFormat()

{

if (_inputDateFormat == null)

{

string df = DateFormat;

if (!df.Contains("MMM"))

df = df.Replace("MM", "M");

if (!df.Contains("ddd"))

df = df.Replace("dd", "d");

// Note: do not replace Replace("tt", "t") because a single "t" will not accept "AM" or "PM".

_inputDateFormat = df.Replace("hh", "h").Replace("HH", "H").Replace("mm", "m").Replace("ss", "s");

}

return _inputDateFormat;

}

public DateTime MinimumDate

{

get { return Convert.ToDateTime(GetValue(MinimumDateProperty)); }

set { SetValue(MinimumDateProperty, value); }

}

public DateTime MaximumDate

{

get { return Convert.ToDateTime(GetValue(MaximumDateProperty)); }

set { SetValue(MaximumDateProperty, value); }

}

#endregion

#region "Events"

public event RoutedEventHandler DateChanged

{

add { AddHandler(DateChangedEvent, value); }

remove { RemoveHandler(DateChangedEvent, value); }

}

public static readonly RoutedEvent DateChangedEvent = EventManager.RegisterRoutedEvent("DateChanged", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(DateTimePicker));

public event RoutedEventHandler DateFormatChanged

{

add { this.AddHandler(DateFormatChangedEvent, value); }

remove { this.RemoveHandler(DateFormatChangedEvent, value); }

}

public static readonly RoutedEvent DateFormatChangedEvent = EventManager.RegisterRoutedEvent("DateFormatChanged", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(DateTimePicker));

#endregion

#region "DependencyProperties"

public static readonly DependencyProperty DateFormatProperty = DependencyProperty.Register("DateFormat", typeof(string), typeof(DateTimePicker), new FrameworkPropertyMetadata("yyyy-MM-dd HH:mm", OnDateFormatChanged));

public static DependencyProperty MaximumDateProperty = DependencyProperty.Register("MaximumDate", typeof(DateTime), typeof(DateTimePicker), new FrameworkPropertyMetadata(Convert.ToDateTime("3000-01-01 00:00"), null, new CoerceValueCallback(CoerceMaxDate)));

public static DependencyProperty MinimumDateProperty = DependencyProperty.Register("MinimumDate", typeof(DateTime), typeof(DateTimePicker), new FrameworkPropertyMetadata(Convert.ToDateTime("1900-01-01 00:00"), null, new CoerceValueCallback(CoerceMinDate)));

public static readonly DependencyProperty SelectedDateProperty = DependencyProperty.Register("SelectedDate",

typeof(DateTime), typeof(DateTimePicker),

new FrameworkPropertyMetadata(DateTime.Now,

new PropertyChangedCallback(OnSelectedDateChanged),

new CoerceValueCallback(CoerceDate)));

/// <summary>true when user is busy editing DateDisplay and the SelectedDate

/// becomes different from the date shown on the text box.</summary>

public static readonly DependencyProperty DateTextIsWrongProperty = DependencyProperty.Register("DateTextIsWrong", typeof(bool), typeof(DateTimePicker), new FrameworkPropertyMetadata(false));

protected bool DateTextIsWrong

{

get { return (bool)GetValue(DateTextIsWrongProperty); }

set { SetValue(DateTextIsWrongProperty, value); }

}

#endregion

#region "EventHandlers"

bool _forceTextUpdateNow = true;

private void CalDisplay_SelectedDatesChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)

{

PopUpCalendarButton.IsChecked = false;

TimeSpan timeOfDay = TimeSpan.Zero;

timeOfDay = SelectedDate.TimeOfDay;

SelectedDate = CalDisplay.SelectedDate.Value.Date + timeOfDay;

}

private void DateDisplay_PreviewMouseUp(object sender, System.Windows.Input.MouseButtonEventArgs e)

{

if (DateDisplay.SelectionLength == 0)

FocusOnDatePart(DateDisplay.SelectionStart);

}

bool IsDateInExpectedFormat()

{

return ParseDateText(false) != null;

}

DateTime? ParseDateText(bool flexible)

{

DateTime selectedDate;

if (!DateTime.TryParseExact(DateDisplay.Text, InputDateFormat(), null, DateTimeStyles.AllowWhiteSpaces, out selectedDate))

if (!flexible || !DateTime.TryParse(DateDisplay.Text, out selectedDate))

return null;

return selectedDate;

}

void ReformatDateText()

{

// Changes DateDisplay.Text to match the current DateFormat

DateTime? date = ParseDateText(true);

if (date != null)

{

string newText = date.Value.ToString(DateFormat);

if (DateDisplay.Text != newText)

DateDisplay.Text = newText;

}

private void DateDisplay_LostFocus(object sender, System.Windows.RoutedEventArgs e)

{

DateDisplay.Text = SelectedDate.ToString(DateFormat);

// When the user selects a field again, then the box loses focus, then

// the user clicks the same field again, the selection is cleared,

// causing the arrows not to appear. To fix, clear selection in advance.

try {

DateDisplay.SelectionLength = 0;

} catch(NullReferenceException) {

// Occurs during shutdown. Bug in WPF? Ain't documented, that's for sure.

}

void DateDisplay_TextChanged(object sender, TextChangedEventArgs e)

{

DateTime? date = ParseDateText(true);

if (date != null)

SelectedDate = date.Value;

}

private void DateTimePicker_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)

{

int selstart = DateDisplay.SelectionStart;

if (!IsDateInExpectedFormat())

return;

switch (e.Key)

{

case Key.Up:

OnUpDown(+1);

break;

case Key.Down:

OnUpDown(-1);

break;

case Key.Left:

if (Keyboard.Modifiers != ModifierKeys.None)

return;

SelectPosition(selstart, Direction.Previous);

break;

case Key.Right:

if (Keyboard.Modifiers != ModifierKeys.None)

return;

SelectPosition(selstart, Direction.Next);

break;

case Key.Tab:

var dir = Direction.Next;

if ((Keyboard.Modifiers & ModifierKeys.Shift) != 0)

dir = Direction.Previous;

e.Handled = SelectPosition(selstart, dir);

break;

default:

char nextChar = '';

if (selstart < DateDisplay.Text.Length)

nextChar = DateDisplay.Text[selstart];

if ((e.Key == Key.OemMinus || e.Key == Key.Subtract || e.Key == Key.OemQuestion || e.Key == Key.Divide) &&

(nextChar == '/' || nextChar == '-') ||

e.Key == Key.Space && nextChar == ' ' ||

e.Key == Key.OemSemicolon && nextChar == ':')

SelectPosition(selstart, Direction.Next);

else

return;

break;

}

e.Handled = true;

}

private void OnUpDown(int increment)

{

int selstart = DateDisplay.SelectionStart;

_forceTextUpdateNow = true;

SelectedDate = Increase(selstart, increment);

FocusOnDatePart(selstart);

}

private static object CoerceDate(DependencyObject d, object value)

{

DateTimePicker me = (DateTimePicker)d;

DateTime current = Convert.ToDateTime(value);

if (current < me.MinimumDate)

current = me.MinimumDate;

if (current > me.MaximumDate)

current = me.MaximumDate;

return current;

}

private static object CoerceMinDate(DependencyObject d, object value)

{

DateTimePicker me = (DateTimePicker)d;

DateTime current = Convert.ToDateTime(value);

if (current >= me.MaximumDate)

throw new ArgumentException("MinimumDate can not be equal to, or more than maximum date");

if (current > me.SelectedDate)

me.SelectedDate = current;

return current;

}

private static object CoerceMaxDate(DependencyObject d, object value)

{

DateTimePicker me = (DateTimePicker)d;

DateTime current = Convert.ToDateTime(value);

if (current <= me.MinimumDate)

throw new ArgumentException("MaximimumDate can not be equal to, or less than MinimumDate");

if (current < me.SelectedDate)

me.SelectedDate = current;

return current;

}

public static void OnDateFormatChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)

{

var me = (DateTimePicker)obj;

me._inputDateFormat = null; // will be recomputed on-demand

me.DateDisplay.Text = me.SelectedDate.ToString(me.DateFormat);

}

public static void OnSelectedDateChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)

{

var me = (DateTimePicker)obj;

var date = (DateTime)args.NewValue;

me.CalDisplay.SelectedDate = date;

me.CalDisplay.DisplayDate = date;

if (me.DateDisplay.IsFocused && !me._forceTextUpdateNow)

{

DateTime? oldDate = me.ParseDateText(true);

if (oldDate != null)

me.DateTextIsWrong = date != oldDate.Value;

}

else

{

me.DateTextIsWrong = false;

me._forceTextUpdateNow = false;

me.DateDisplay.Text = date.ToString(me.DateFormat);

}

#endregion

// Selects next or previous date value, depending on the incrementor value

// Alternatively moves focus to previous control or the calender button

private bool SelectPosition(int selstart, Direction direction)

{

selstart = CalcPosition(selstart, direction);

if (selstart > -1)

{

return FocusOnDatePart(selstart);

}

else

return false;

}

static char At(string s, int index)

{

if ((uint)index < (uint)s.Length)

return s[index];

return '';

}

// Gets location of next/previous date field, depending on the incrementor value.

// Returns -1 if there is no next/previous field.

private int CalcPosition(int selStart, Direction direction)

{

string df = DateFormat;

if (selStart >= df.Length)

selStart = df.Length - 1;

char startChar = df[selStart];

int i = selStart;

for (; ; )

{

i += (int)direction;

if ((uint)i >= (uint)df.Length)

return -1;

if (df[i] == startChar)

continue;

if (char.IsLetter(df[i]))

break;

startChar = ''; // to handle cases like "yyyy-MM-dd (ddd)" correctly

}

if (direction < 0)

// move to the beginning of the field

while (i > 0 && df[i - 1] == df[i])

i--;

return i;

}

private bool FocusOnDatePart(int selStart)

{

ReformatDateText();

// Find beginning of field to select

string df = DateFormat;

if (selStart > df.Length - 1)

selStart = df.Length - 1;

char firstchar = df[selStart];

while (!char.IsLetter(firstchar) && selStart + 1 < df.Length)

{

selStart++;

firstchar = df[selStart];

}

while (selStart > 0 && df[selStart - 1] == firstchar)

selStart--;

int selLength = 1;

while (selStart + selLength < df.Length && df[selStart + selLength] == firstchar)

selLength++;

// don't select AM/PM: we have no interface to change it.

if (firstchar == 't')

return false;

DateDisplay.Focus();

DateDisplay.Select(selStart, selLength);

return true;

}

private DateTime Increase(int selstart, int value)

{

DateTime retval = (ParseDateText(false) ?? SelectedDate);

try

{

switch (DateFormat.Substring(selstart, 1))

{

case "h":

case "H":

retval = retval.AddHours(value);

break;

case "y":

retval = retval.AddYears(value);

break;

case "M":

retval = retval.AddMonths(value);

break;

case "m":

retval = retval.AddMinutes(value);

break;

case "d":

retval = retval.AddDays(value);

break;

case "s":

retval = retval.AddSeconds(value);

break;

}

catch (ArgumentException ex)

{

//Catch dates with year over 9999 etc, dont throw

}

return retval;

}

// Adorners must subclass the abstract base class Adorner.

public class TextBoxUpDownAdorner : Adorner

{

StreamGeometry _triangle = new StreamGeometry();

bool _shown;

double _x, _top, _bottom;

public Pen Outline = new Pen(new SolidColorBrush(Color.FromArgb(64,255,255,255)), 5);

public Brush Fill = Brushes.Black;

public TextBoxUpDownAdorner(TextBox adornedBox) : base(adornedBox)

{

_triangle = new StreamGeometry();

_triangle.FillRule = FillRule.Nonzero;

using (StreamGeometryContext c = _triangle.Open())

{

c.BeginFigure(new Point(-10, 0), true /* filled */, true /* closed */);

c.LineTo(new Point(10, 0), true, false);

c.LineTo(new Point(0, 15), true, false);

}

_triangle.Freeze();

MouseDown += (s, e) => {

if (Click != null)

{

bool up = e.GetPosition(AdornedElement).Y < (_top + _bottom) / 2;

Click((TextBox)AdornedElement, up ? 1 : -1);

}

};

adornedBox.LostFocus += RelevantEventOccurred;

adornedBox.SelectionChanged += RelevantEventOccurred;

}

void RelevantEventOccurred(object sender, RoutedEventArgs e)

{

// In OnRender, GetRectFromCharacterIndex may return Infinity values,

// so measure the location of the selection here instead.

var box = AdornedElement as TextBox;

if (box.IsFocused) {

int start = box.SelectionStart, len = box.SelectionLength;

if (_shown = len > 0) {

var rect1 = box.GetRectFromCharacterIndex(start);

var rect2 = box.GetRectFromCharacterIndex(start + len);

_top = rect1.Top - 2;

_bottom = rect1.Bottom + 2;

_x = (rect1.Left + rect2.Left) / 2;

}

} else

_shown = false;

InvalidateVisual();

}

public event Action<TextBox, int> Click;

// A common way to implement an adorner's rendering behavior is to override the OnRender

// method, which is called by the layout system as part of a rendering pass.

protected override void OnRender(DrawingContext drawingContext)

{

if (_shown)

{

drawingContext.PushTransform(new TranslateTransform(_x, _top));

drawingContext.PushTransform(new ScaleTransform(1, -1));

drawingContext.DrawGeometry(Fill, Outline, _triangle);

drawingContext.Pop();

drawingContext.PushTransform(new TranslateTransform(_x, _bottom));

drawingContext.DrawGeometry(Fill, Outline, _triangle);

drawingContext.Pop();

}

]

public class BoolInverter : MarkupExtension, IValueConverter

{

public override object ProvideValue(IServiceProvider serviceProvider)

{ return this; }

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)

{ return !(bool)value; }

public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)

{

return !(bool)value;

}

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