Binding a Value of a Custom Dependancy Property Silverlight

Question

I have setted a property like this:

        public static readonly DependencyProperty ValorRegistadoProperty = DependencyProperty.RegisterAttached(
        "ValorRegistado",
        typeof(string),
        typeof(CampoInfo), new PropertyMetadata(new PropertyChangedCallback((d, e) =>
        {
            System.Diagnostics.Debug.WriteLine("Valor mudado");
        })));
    public static void SetValorRegistado(UIElement element, string value)
    {
        if (string.IsNullOrEmpty(value.Trim()))
            throw new Exception("Por favor preencha este valor.");
        element.SetValue(ValorRegistadoProperty, value);
    }
    public static string GetValorRegistado(UIElement element)
    {
        return (string)element.GetValue(ValorRegistadoProperty);
    }

And have the control declared like this:

<toolkit:NumericUpDown Value="{Binding (CampoInfo.ValorRegistado), Mode=TwoWay}">

I know I heve to user a converter, but this doens't give me any error anyway....

How do you bind custom dependency properties?

Answer 1

What you have should work, I have similar working, for instance:

public static string GetId ( DependencyObject target )
{
    return ( ( target.GetValue( IdProperty ) ) as string );
}

public static void SetId ( DependencyObject target, string value )
{
    target.SetValue( IdProperty, value );
}

public static readonly DependencyProperty IdProperty = DependencyProperty.RegisterAttached(
    "SamplePropertyName",
    typeof( string ),
    typeof( Translatable ),
    new PropertyMetadata( IdPropertyChanged ) );

Which is bound as:

<TextBlock TextWrapping="Wrap" mystuff:myclass.Id="{Binding FooBar.Id}"/>

The only part of your binding I would try and change is:

<toolkit:NumericUpDown Value="{Binding CampoInfo.ValorRegistado, Mode=TwoWay"/>

I would check that the binding expression is working, for example, maybe you only need to specify ValorRegistado in the above example. One way of checking is to try binding to a simple TextBlock to prove that a value is coming through or to bind CampoInfo and see a fully qualified object name show.

Another approach to try binding the dependency property is to name the page you are using and use element binding, for example:

In your XAML page definition:

<UserControl 
    x:Name="myPageIdentifier"
    x:Class="MyTest.MyPage"
    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"
    mc:Ignorable="d"
    d:DesignHeight="300" 
    d:DesignWidth="400">

....

</UserControl>

Then do the binding as:

<toolkit:NumericUpDown Value="{Binding ElementName=myPageIdentifier,Path=SamplePropertyName,Mode=TwoWay"/>

Answer 2

I implemented the property changed this way:

        public static readonly DependencyProperty ValorRegistadoProperty = DependencyProperty.RegisterAttached(
        "ValorRegistado",
        typeof(string),
        typeof(CampoInfo), new PropertyMetadata(new PropertyChangedCallback((d, e) =>
        {
            UIElement uie = (UIElement)d;
            SetValorRegistado(uie, e.NewValue.ToString());
        })));

And binding:

local:CampoInfo.ValorRegistado="{Binding RelativeSource={RelativeSource Self}, Path=Value, Mode=TwoWay}"