自定义控件派生自具有内部控件和属性的控件

Question

I have this control as an example:

Generic.xaml

<Style TargetType="{x:Type local:EditLabel}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type local:EditLabel}" >
                <StackPanel Name ="PART_SPPrincipal" VerticalAlignment="Center" Orientation="Horizontal"  >
                    <TextBox Name="PART_TextBox" Width="100" HorizontalAlignment="Left" />
                    <Label Name="PART_Label" BorderBrush="Black" BorderThickness="1"
                           HorizontalAlignment="Stretch" VerticalAlignment="Stretch"  />
                </StackPanel>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

EditLabel.cs

public class EditLabel : UserControl
{

    static EditLabel()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(EditLabel), new FrameworkPropertyMetadata(typeof(EditLabel)));
    }


    private Label _label;

    public static readonly  DependencyProperty LabelWidthProperty = DependencyProperty.Register("LabelWidth", typeof(int), typeof(EditLabel),
        new FrameworkPropertyMetadata(10, FrameworkPropertyMetadataOptions.AffectsRender));



    [Description("Establece el ancho de la etiqueta de descripción"), Category("Lutx")]
    public int LabelWidth
    {
        get
        {
            return (int)GetValue(LabelWidthProperty);
        }

        set
        {
            SetValue(LabelWidthProperty, value);
            _label.Width = value;               
        }
    }
    public override void OnApplyTemplate()
    {
        //_txtBox = GetTemplateChild("PART_TextBox") as ButtonEdit;

        _label = GetTemplateChild("PART_Label") as Label;
    }
}    

The problem is nothing happens when I change LabelWidth, I've tried these ways:
1) In design time when I change LabelWidth nothing happens, if I put a breakpoint at line:
_label.Width = value;
never stop there in execution time

2)I thing maybe the problem is i try to do it from code, and when tried in Generic.xaml in Label line: <Label Name="PART_Label" Width="{Binding LabelWith}"...
nothing happens

3) When i place the control in a window

    <local:EditLabel  LabelWidth="30"/>

nothing happens

I've not more ideas at this time so your help will be really appreciated

Answer 1

In the declaration of your LabelWidthProperty (DependencyProperty) put a callback in your PropertyMetadata and set the _label.Width to e.NewValue . That should fix your problem. Remove the _label.Width = value; from LabelWidth

Answer 2

Thank's TYY I cannot vote up you because i have not 15 reputation.

Yes seems the right way but the problem is PropertyChangedCallback must be declared as static and not is an instance's part, so after changes see the code. Always exception because _label is null. See the new code (OnLabelChanged commented lines also tested):

public class EditLabel : UserControl {

    static EditLabel()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(EditLabel), new FrameworkPropertyMetadata(typeof(EditLabel)));
    }


    private Label _label;

    public Label Label
    {
        get { return _label; }
        set { _label = value; }
    }

    public static readonly  DependencyProperty LabelWidthProperty = DependencyProperty.Register("LabelWidth", typeof(int), typeof(EditLabel), 
                                                                    new PropertyMetadata(10, new PropertyChangedCallback(OnLabelChanged)));



    [Description("Establece el ancho de la etiqueta de descripción"), Category("Lutx")]
    public int LabelWidth
    {
        get
        {
            return (int)GetValue(LabelWidthProperty);
        }

        set
        {
            SetValue(LabelWidthProperty, value);          
        }
    }


    private static void OnLabelChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
       EditLabel el  = obj as EditLabel;
       el.Label.Width = (int)e.NewValue;

       //Label lbl = el.GetTemplateChild("PART_Label") as Label;
       //lbl.Width(int)e.NewValue;          

     }

    public override void OnApplyTemplate()
    {
        //_txtBox = GetTemplateChild("PART_TextBox") as ButtonEdit;

        _label = GetTemplateChild("PART_Label") as Label;


        SetBinding(LabelWidthProperty, new Binding
                        {
                            Source = _label,
                            Path = new PropertyPath("Width")
                        });
    }
}