依赖项属性绑定未更新

Question

I have defined a dependency propery as follows:

public static readonly DependencyProperty AnimateColumnWidthProperty =
    DependencyProperty.Register("AnimateColumnWidthProperty", typeof(double), typeof(MainWindow), new PropertyMetadata(0.0));

public double AnimateColumnWidth
{
    get { return (double)GetValue(AnimateColumnWidthProperty); }
    set { SetValue(AnimateColumnWidthProperty, value); }
}

When my application starts I do this....

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    AnimateColumnWidth = Properties.Settings.Default.ProductInfoWidthExpanded;
}

... which should initialise the value to its starting value - in this case 400.

I have then bound a column of a grid in my UI to this property...

<ColumnDefinition 
    Name="ProductInfo" 
    Width="{Binding Path=AnimateColumnWidth,
                    Converter={StaticResource doubleToGridLength},
                    Mode=TwoWay}" />

As I understand it, as the column width is bound to this property, whenever I update the property the column width should also update.

What am I doing wrong as the width does not update when I change the property? I am also trying to update it via an animation which also doesnt work. Additionally, a breakpoint set on the getter of the AnimateColumnWidth property is never hit - meaning that nothing ever tried to retrieve the property.

(This did work so clearly I have broken something somewhere!!)

Footnote:

The value converted is defined in the root namespace of my app (I believe that WPF would complain if it couldnt find it).

[ValueConversion(typeof(Double), typeof(GridLength))]
public class DoubleToGridLength : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return new GridLength((double)value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return ((GridLength)value).Value;
    }
}

Answer 1

You register the property as "AnimateColumnWidthProperty" , which is "wrong", only the field name is arbitrary, you probably want "AnimateColumnWidth" (or you change the binding of course, but as is, it fails since the path points to an unregistered property).

You might want to read something on debugging bindings as well, then you can spot such errors as they will be reported by the binding engine. (something like "property x not found on object y").

Also using breakpoints in the getters or setters does not tell you anything, the binding engine does not use them, they are just for your own convenience.

Answer 2

One thing I hadnt done was set the datacontext of the grid who's column I wanted to affect to "this".

public MainWindow()
{
    InitializeComponent();
    ProductsArea.DataContext = this;
}