// Replace [TYPE] with your property type
// Replace [NAME] with your property name
public [TYPE] [NAME]
{
    get
    {
        return ([TYPE])GetValue([NAME]Property);
    }
    set
    {
        SetValue([NAME]Property, value);
    }
}

public static readonly DependencyProperty [NAME]Property = DependencyProperty.Register("[NAME]", typeof([TYPE]), typeof(EditableTextBlock), new PropertyMetadata([DEPEND ON THE TYPE]);
// For more informations about PropertyMetadata and DependencyProperty
// Read : http://msdn.microsoft.com/en-us/library/system.windows.dependencyproperty.aspx