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  • Wpf binding to a function

    - by carlopenid
    I've a created a simple scrollviewer (pnlDayScroller) and want to have a separate horizontal scrollbar (associated scroller) to do the horizontal scrolling. All works with the below code accept I need to bind the visibility of the associated scroller. I can't simply bind this to the visibility property of the horizontal template part of the scroll viewer as I've set this to be always hidden. The only way I can think to do this is to bind the visibility of the associated scroller to a function such that If associatedScroller.scrollableWidth > 0 then associatedScroller.visibility = visibility.visible else associatedScroller.visibility = visibility.collapsed end if Is this possible to do and if so how do I do it? Private Sub pnlDayScroller_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles pnlDayScroller.Loaded Dim binViewport, binMax, binMin, binSChange, binLChange As Binding Dim horizontalScrollBar As Primitives.ScrollBar = CType(pnlDayScroller.Template.FindName("PART_HorizontalScrollBar", pnlDayScroller), Primitives.ScrollBar) binViewport = New Binding("ViewportSize") binViewport.Mode = BindingMode.OneWay binViewport.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.ViewportSizeProperty, binViewport) binMax = New Binding("Maximum") binMax.Mode = BindingMode.OneWay binMax.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.MaximumProperty, binMax) binMin = New Binding("Minimum") binMin.Mode = BindingMode.OneWay binMin.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.MinimumProperty, binMin) binSChange = New Binding("SmallChange") binSChange.Mode = BindingMode.OneWay binSChange.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.SmallChangeProperty, binSChange) binLChange = New Binding("LargeChange") binLChange.Mode = BindingMode.OneWay binLChange.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.LargeChangeProperty, binLChange) End Sub Private Sub associatedScroller_Scroll(ByVal sender As System.Object, ByVal e As System.Windows.RoutedPropertyChangedEventArgs(Of Double)) Handles associatedScroller.ValueChanged pnlDayScroller.ScrollToHorizontalOffset(e.NewValue) end sub FOLLOW UP (thanks to JustABill) : I've add this code into the pnlDayScroller sub above (I've discovered scrollableWidth is a property of scrollviewer not scrollbar, but the maximum property gives a result I can use instead) binVisibility = New Binding("Maximum") binVisibility.Mode = BindingMode.OneWay binVisibility.Source = horizontalScrollBar binVisibility.Converter = New ScrollableConverter associatedScroller.SetBinding(Primitives.ScrollBar.VisibilityProperty, binVisibility) and I've created this class Public Class ScrollableConverter Implements IValueConverter Public Function Convert(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.Convert Dim dblMaximum As Double If targetType IsNot GetType(Visibility) Then Throw New InvalidOperationException("The target must be a visibility") Else dblMaximum = CType(value, Double) Debug.WriteLine("Value of double is " & dblMaximum) If dblMaximum > 0 Then Return Visibility.Visible Else Return Visibility.Collapsed End If End If End Function Public Function ConvertBack(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack Throw New NotSupportedException() End Function End Class And the problem is resolved.

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