[TemplatePart(Name = "PART_TextBox", Type = typeof(TextBox))]
    ...
    public class MyControl : Control
    {
        public static readonly DependencyProperty TextProperty =
            DependencyProperty.Register("Text", typeof(String), typeof(MyControl),
            new UIPropertyMetadata(null, new PropertyChangedCallback(OnTextChanged)));

        public static readonly RoutedEvent TextChangedEvent =
            EventManager.RegisterRoutedEvent("TextChanged", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(MyControl));

        private static void OnTextChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            MyControl textBox = o as MyControl;
            if (textBox != null)
                textBox.OnTextChanged((String)e.OldValue, (String)e.NewValue);
        }

        protected virtual void OnTextChanged(String oldValue, String newValue)
        {
            this.RaiseEvent(new RoutedEventArgs(MyControl.TextChangedEvent, this));
        }

        public String Text
        {
            get { return (String)GetValue(TextProperty); }
            set { SetValue(TextProperty, value); }
        }

        public event RoutedEventHandler TextChanged
        {
            add { AddHandler(TextChangedEvent, value); }
            remove { RemoveHandler(TextChangedEvent, value); }
        }

        ... разное другое
    }

    <Style TargetType="{x:Type local: MyControl}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type local: MyControl }">
                    <Border Background="{TemplateBinding Background}"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}">
                        <DockPanel LastChildFill="True" >

                            ...

                            <TextBox x:Name="PART_TextBox" 
                                     Text="{Binding Path=Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, RelativeSource={RelativeSource TemplatedParent}}"
                                     BorderBrush="{x:Null}" BorderThickness="0" VerticalAlignment="Center" />
                        </DockPanel>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

<MyControls:MyControl Text="{Binding Path=MyClass.Text, UpdateSourceTrigger=PropertyChanged, RelativeSource={...}}" /> 

<TextBox Text="{Binding Path=MyClass.Text, UpdateSourceTrigger=PropertyChanged, RelativeSource={...}}" />

        public static readonly DependencyProperty TextProperty =
            DependencyProperty.Register("Text", typeof(String), typeof(TextBoxButton),
            new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, new PropertyChangedCallback(OnTextChanged)));

<MyControls:MyControl Text="{Binding Path=MyClass.Text, UpdateSourceTrigger=PropertyChanged, RelativeSource={...}}" /> 

<MyControls:MyControl Text="{Binding Path=MyClass.Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, RelativeSource={...}}" />