WPF Binding to a custom property in a custom control

Question

I have a custom text box defined as follows: ``` public class CustomTextBox : TextBox { public static DependencyProperty CustomTextProperty = DependencyProperty.Register("CustomText", typeof(string), typeof(CustomTextBox)); static CustomTextBox() { TextProperty.OverrideMetadata(typeof(SMSTextBox), new FrameworkPropertyMetadata(string.Empty, FrameworkPropertyMetadataOptions.Journal | FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, new PropertyChangedCallback(CustomTextBox_OnTextPropertyChanged)); } public string CustomText { get { return (string)GetValue(CustomTextProperty); } set { SetValue(CustomTextProperty, value); } } private static void CustomTextBox_OnTextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { CustomTextBox customTextBox = d as CustomTextBox; customTextBox.SetValue(CustomTextProperty, e.NewValue); } } ``` I'm binding the Custom Text property in the XAML - ``` <local:CustomTextBox CustomText="{Binding ViewModelProperty}" /> ``` The prob…

Accepted Answer

I guess the binding needs to be two-way.

```
<local:CustomTextBox
    CustomText="{Binding ViewModelProperty, Mode=TwoWay}" />
```

You wouldn't need to specify the `Mode` if you made the `CustomText` property bind two-way by default:

```
public static readonly DependencyProperty CustomTextProperty =
    DependencyProperty.Register(
        "CustomText", typeof(string), typeof(CustomTextBox),
        new FrameworkPropertyMetadata(
            FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
```

You may also have to define a PropertyChangedCallback for the `CustomText` property that updates the `Text` property (i.e. the other direction of what you have implemented now). Otherwise the TextBox won't display anything that is initially contained in the ViewModel property and of course woudln't be updated when the ViewModel property changes.

WPF Binding to a custom property in a custom control

Solution

Problem