Binding the width property with a multibinding gives a width of zero
.net, wpf, wpf-controls
Solution
If you run this example in Debug, the Output window in visual studio will show you the following error:
System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='100' MultiBindingExpression:target element is 'Border' (Name=''); target property is 'Width' (type 'Double')
The error text explains the issue, the value returned by your Converter is not `Double`. Change your return statement to `return 100.0;` and see the result.
Problem
I have a problem binding the "width" property of a border control. When i bind it with a constant, the change is reflected in runtime, but when i bound it with a converter fails, even if the converter return the same value than the constant. Here is the user control. The problem is with the "Border" object. If i do this, the control works as spected: ``` <UserControl.Resources> <DataTemplate x:Key="DataTemplateHeat"> <Border Margin="1,0,0,0" BorderBrush="Black" BorderThickness="1" Width="100"> </Border> </DataTemplate> </UserControl.Resources> <DockPanel> <ItemsControl x:Name="CnvHeats" ItemsSource="{Binding}" ItemTemplate="{StaticResource DataTemplateHeat}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <StackPanel Orientation="Horizontal" Background="Red" /> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> </ItemsControl> </DockPanel> </UserControl> ``` but if i do this, the control fails. The converter executes the correct number of times, and the parameters are ok, but it fails even if i hardcode a return value: ``` <UserControl.Resources> <DataTemplate x:Key="DataTemplateHeat"> <Border Margin="1,0,0,0" BorderBrush="Black" BorderThickness="1"> <Border.Width> <MultiBinding Converter="{StaticResource proportionalWidthConverter}" > <Binding Mode="OneWay" Path="GraphProportion" /> <Binding Mode="OneWay" Path="ActualWidth" RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type StackPanel}, AncestorLevel=1}"/> </MultiBinding> </Border.Width> </Border> </DataTemplate> </UserControl.Resources> <DockPanel> <ItemsControl x:Name="CnvHeats" ItemsSource="{Binding}" ItemTemplate="{StaticResource DataTemplateHeat}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <StackPanel Orientation="Horizontal" Background="Red" /> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> </ItemsControl> </DockPanel> </UserControl> ``` and here is the converter: ``` public class ProportionalWidthConverter : IMultiValueConverter { public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture) { return 100; } public object[] ConvertBack( object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture) { throw new NotImplementedException(); } } ``` Any help is apreciated. Thank you in advance.