WPF DependencyProperty expose a control property

Question

I have a UserControl with a TextBox and I want to expose TextBox.Text property. We must take into consideration that TextBox.Text and the DependencyProperty binded to it, are not always the same values. And I explain it a little bit deeper:

<UserControl x:Class="MySolution.MyUserControl"
             Name="MyControl"
             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="450" d:DesignWidth="800">
    <StackPanel>
        <TextBlock>This is my label</TextBlock>
        <TextBox x:Name="myTextBox" Text="{Binding ElementName=MyControl, Path=BindingText, UpdateSourceTrigger=LostFocus}"></TextBox>
    </StackPanel>
</UserControl>

And this code-behind:

using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
namespace MySolution
{
    public partial class MyUserControl : UserControl
    {
        public MyUserControl()
        {
            InitializeComponent();
        }

        public string BindingText
        {
            get { return (string)GetValue(BindingTextProperty); }
            set { SetValue(BindingTextProperty, value); }
        }

        public static readonly DependencyProperty BindingTextProperty =
            DependencyProperty.Register(nameof(BindingText), typeof(string), typeof(MyUserControl),
                new FrameworkPropertyMetadata(null)
                {
                    BindsTwoWayByDefault = true
                });
}

In this simple example, if we run the application and we type "Hello" in myTextBox and we do not lose the focus , we would have that TextBox.Text is "Hello", but BindingText (our DependencyProperty) is still empty (until we lose the focus and the binding updates).

In other words, what I would like is to be able to bind to something like this:

public string Text
{
    get => myTextBox.Text;
    set => myTextBox.Text = value;
}

But I this does not work, I guess because it is not a DependencyProperty. Is it possible to create a DependencyProperty that exposes myTextBox.Text anyway?

Answer 1

From my limited testing, this solution appears to be sufficient for your needs

Code behind:

public partial class MyUserControl
{
    public MyUserControl()
    {
        InitializeComponent();
    }
    public string Text
    {
        get => myTextBox.Text;
        set
        {
            Box.Text = value;
            SetValue(TextProperty, value);
        }
    }
    public static readonly DependencyProperty TextProperty =
        DependencyProperty.Register(nameof(Text), typeof(string), typeof(testControl1),
            new PropertyMetadata(default(string)));
}

XAML:

 <StackPanel>
    <TextBlock>This is my label</TextBlock>
    <TextBox x:Name="myTextBox" Text="{Binding ElementName=MyControl,Path=Text, Mode=OneWay}"/>
</StackPanel>