WPF user control binding not worked

Question

Hi dears,
I created an user control in my WPF app.
When I want to bind a data to my control it's not working.

my user control :

<UserControl x:Class="StoreManager.UserControls.DateTimePicker2"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             mc:Ignorable="d" 
             d:DesignHeight="100" d:DesignWidth="300" >
    <Grid>
        <TextBox x:Name="myTextBox" TextChanged="myTextBox_TextChanged"/>
    </Grid>
</UserControl>


public partial class DateTimePicker2 : UserControl
{
        public DateTimePicker2()
        {
            InitializeComponent();
        }

        public static readonly DependencyProperty SelectedDateProperty = DependencyProperty.Register(nameof(SelectedDate), typeof(DateTime), typeof(DateTimePicker2), new PropertyMetadata(DateTime.Now));

        public DateTime SelectedDate
        {
            get { return (DateTime)GetValue(SelectedDateProperty); }
            set
            {
                SetValue(SelectedDateProperty, value);
                if(!IsSettingDateTime)
                    myTextBox.Text = value.ToShortDateString();
            }
        }

        private bool IsSettingDateTime=false;    
        private void myTextBox_TextChanged(object sender, TextChangedEventArgs e)
        {
            IsSettingDateTime=true;
            SelectedDate = DateTime.Parse(myTextBox.Text);
            IsSettingDateTime=false;
        }
}

my window :

 <Window x:Class="StoreManager.frmSample"
        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:StoreManager"
        mc:Ignorable="d"
        xmlns:userControl="clr-namespace:StoreManager.UserControls"
        Title="MainWindow" Height="400" Width="800" FlowDirection="RightToLeft" WindowStartupLocation="CenterScreen">
    <Window.DataContext>
        <local:DateHelper/>
    </Window.DataContext>
    <Grid FlowDirection="RightToLeft" >
        <StackPanel>
            <userControl:DateTimePicker2 x:Name="myControl" SelectedDate="{Binding dateTime,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Height="60" Width="300"/>
            <Button Content="Add 10 Days" Click="Button_Click" Margin="10" Width="300"/>
        </StackPanel>
    </Grid>
</Window>


namespace StoreManager
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class frmSample : Window
    {
        DateHelper dtContext;
        public frmSample()
        {
            InitializeComponent();
            dtContext = (DateHelper)DataContext;
            dtContext.dateTime = System.DateTime.Now;
            dtContext.myString = "Date";
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            dtContext.dateTime= dtContext.dateTime.AddDays(10);
            dtContext.myString = dtContext.dateTime.ToShortDateString();
        }
    }

    public class DateHelper: INotifyPropertyChanged
    {
        private DateTime _dateTime;
        public DateTime dateTime
        {
            get { return _dateTime; }
            set
            {
                _dateTime = value;
                OnPropertyChanged(nameof(dateTime));
            }
        }

        private string _myString;
        public string myString
        {
            get { return _myString; }
            set
            {
                _myString = value;
                OnPropertyChanged(nameof(myString));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        public virtual void OnPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

    }
}

Answer 1

You could use the following code.
UserControl.xaml:

 <Grid>  
        <TextBox x:Name="myTextBox" Text="{Binding SelectedDate,  
                RelativeSource={RelativeSource AncestorType=UserControl}}"/>  
    </Grid>  

UserControl.xaml.cs:

using System;  
using System.Windows;  
using System.Windows.Controls;  

namespace UserControlWorking  
{  
  public partial class DateTimePicker2 : UserControl  
  {  
    public DateTimePicker2()  
    {  
      InitializeComponent();  
    }  
    public static readonly DependencyProperty SelectedDateProperty =   
      DependencyProperty.Register(nameof(SelectedDate), typeof(DateTime), typeof(DateTimePicker2),  
        new FrameworkPropertyMetadata(DateTime.Now, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));  

    public DateTime SelectedDate  
    {  
      get { return (DateTime)GetValue(SelectedDateProperty); }  
      set  
      {  
        SetValue(SelectedDateProperty, value);  

      }  
    }  

  }  
}  

MainWindow.xaml:

<Window.DataContext>  
        <local:DateHelper/>  
    </Window.DataContext>  
    <Grid FlowDirection="RightToLeft" >  
        <StackPanel>  
            <local:DateTimePicker2 x:Name="myControl" SelectedDate="{Binding dateTime,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Height="60" Width="300"/>  
            <Button Content="Add 10 Days" Click="Button_Click" Margin="10" Width="300"/>  
        </StackPanel>  
    </Grid>  

MainWindow.xaml.cs:

using System;  
using System.ComponentModel;  
using System.Windows;  
namespace UserControlWorking  
{  
  public partial class MainWindow : Window  
  {  
    DateHelper dtContext;  
    public MainWindow()  
    {  

      InitializeComponent();  
      dtContext =  new DateHelper();  
      DataContext=dtContext;  
      dtContext.dateTime = System.DateTime.Now;  
      dtContext.myString = "Date";  
    }  
    private void Button_Click(object sender, RoutedEventArgs e)  
    {  
      dtContext.dateTime = dtContext.dateTime.AddDays(10);  
      dtContext.myString = dtContext.dateTime.ToShortDateString();  
    }  
  }  
  public class DateHelper : INotifyPropertyChanged  
  {  
    private DateTime _dateTime;  
    public DateTime dateTime  
    {  
      get { return _dateTime; }  
      set  
      {  
        _dateTime = value;  
        OnPropertyChanged(nameof(dateTime));  
      }  
    }  

    private string _myString;  
    public string myString  
    {  
      get { return _myString; }  
      set  
      {  
        _myString = value;  
        OnPropertyChanged(nameof(myString));  
      }  
    }  

    public event PropertyChangedEventHandler PropertyChanged;  
    public virtual void OnPropertyChanged(string propertyName)  
    {  
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));  
    }  

  }  
}  

The result:

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Answer 2

Its worked for me, but there is a problem.

public DateTime SelectedDate  
     {  
       get { return (DateTime)GetValue(SelectedDateProperty); }  
       set  
       {  
         SetValue(SelectedDateProperty, value);  
         SelectedDate_Changed(null,null);  
       }  
     }  

When I change SelectedDate programmatically it run SelectedDate_Changed(null,null) method correctly, but when SelectedDate change with binding it don't run SelectedDate_Changed(null,null) method.