Databinding one property on a Dialog from two contols - wpf

Question

I have a Window that I'm showing using ShowDialog. One of the values I'm trying to get from the user is size in GB or TB. So I have two controls for this, an IntegerUpDown from the WPF Extended Toolkit and a ComboBox:
<xctk:IntegerUpDown Name="SizeN" Minimum="1" Maximum="1023" Increment="1" Value="100"/>
<ComboBox Name="SizeS" SelectedIndex="0">
<ComboBoxItem>GB</ComboBoxItem>
<ComboBoxItem>TB</ComboBoxItem>
</ComboBox>
I am setting the Dialog's DataContext to itself. I have defined the Capacity property:
public ulong Capacity { get; set; }
public CustomWindow()
{
InitializeComponent();
DataContext = this;
}
I have already created an IMultiValueConverter, PowerConverter, that takes an int and a string and returns ulong. I think the correct MultiBinding is:
<Window.Resources>
<local:PowerConverter x:Key="CapacityConverter" />
</Window.Resources>
<MultiBinding Converter="{StaticResource CapacityConverter}">
<Binding ElementName="SizeN" Path="Value" />
<Binding ElementName="SizeS" Path="SelectedValue" />
</MultiBinding>
I can't figure out how to assign this binding to the Capacity property on the Dialog. I want WPF to automagically set the Capacity property for me. Any ideas?

Answer 1

I had to convert Capacity into a DependencyProperty on CustomWindow, set the SelectedValuePath attribute on the ComboBox, and assign the binding to Capacity in the style.
XAML:
<Window xmlns:="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:xctk="clr-namespace:Xceed.Wpf.Toolkit;assembly=WPFToolkit.Extended"
xmlns:local="clr-namespace:MyProject"
x:Class="MyProject.CustomWindow" Title="CustomWindow"
DataContext="{Binding RelativeSource={RelativeSource Self}}">
<Window.Resources>
<local:PowerConverter x:Key="CapacityConverter" />
</Window.Resources>
<Window.Style>
<Style TargetType="{x:Type local:CustomWindow}">
<Setter Property="Capacity">
<Setter.Value>
<MultiBinding Converter="{StaticResource CapacityConverter}"
Mode="TwoWay">
<Binding ElementName="SizeNumber" Path="Value"
Mode="TwoWay" />
<Binding ElementName="SizeSuffix" Path="SelectedValue"
Mode="TwoWay" />
</MultiBinding>
</Setter.Value>
</Setter>
</Style>
</Window.Style>
<StackPanel>
<xctk:IntegerUpDown Name="SizeNumber" Minimum="1" Maximum="1023" Increment="1"
Value="100"/>
<ComboBox Name="SizeSuffix" SelectedIndex="0" SelectedValuePath="Content">
<ComboBoxItem>GB</ComboBoxItem>
<ComboBoxItem>TB</ComboBoxItem>
</ComboBox>
</StackPanel>
</Window>
Code behind:
public partial class CustomWindow : Window
{
public CustomWindow()
{
InitializeComponent();
}
public static readonly DependencyProperty CapacityProperty =
DependencyProperty.Register("Capacity", typeof(ulong), typeof(CustomWindow));
public ulong Capacity
{
get
{
return (ulong)GetValue(CapacityProperty);
}
set
{
SetValue(CapacityProperty, value);
}
}
}