Question

I have been searching for an answer for this for almost a week now, and I can’t seem to find a way to do this. I would think it is a relatively simple thing…

I have a ListView, and one GridViewColumn contains TextBox items. I want to put a Label right underneath the ListView, and fill it with the sum of the items in all the TextBoxes. Whenever someone changes a value in any of the TextBoxes, the sum should change, too.

I know I need to use a Converter to get the sum… but I don’t know how to get the binding right…

Any help would be greatly appreciated!

EDIT: I ended up solving this in a slightly different way. I will post my solution below.

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:converters="clr-namespace:WpfApplication2"
    Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <XmlDataProvider x:Key="myParties" XPath="Parties" Source="XMLFile1.xml" />
        <CollectionViewSource x:Key="myCollectionViewSource" Source="{StaticResource myParties}" />
        <converters:SumConverter x:Key="mySumConverter" />
    </Window.Resources>

    <StackPanel>
        <Button x:Name="Breakpoint" Click="bpClick" Content="Breakpoint"/>
        <ListView x:Name="myListView" 
                  HorizontalAlignment="Stretch" 
                  ItemsSource="{Binding Source={StaticResource myCollectionViewSource},XPath='Party',Mode=TwoWay}">
            <ListView.View>
                <GridView>
                    <GridViewColumn Width="100" DisplayMemberBinding="{Binding XPath='@Contact'}" Header="Contact"/>
                    <GridViewColumn DisplayMemberBinding="{Binding XPath='@Qty'}" Header="Q"/>
                    <GridViewColumn DisplayMemberBinding="{Binding XPath='@Amount'}" Header="Amt"/>
                    <GridViewColumn x:Name="tbTot" Header="Tot">
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <DockPanel>
                                    <TextBox Width="100" Text="{Binding XPath='@Tot'}" />
                                </DockPanel>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                </GridView>
            </ListView.View>    
        </ListView>

        <Label Height="22">
            <Label.Content>
                <MultiBinding Converter="{StaticResource mySumConverter}">
                    <Binding ElementName="myListView" Path="Items"/>
                    <Binding ElementName="myListView" Path="Items.Count"/>
                </MultiBinding>
            </Label.Content>
        </Label>
    </StackPanel>
</Window>

XML file:

<?xml version="1.0" encoding="utf-8" ?>
<Parties>
  <Party Contact="Jim Shmekel"
         Qty="1"
         Amount="55.00" 
         Tot="55.00"/>
  <Party Contact="Shmi Skywalker"
         Qty="1"
         Amount="20.00" 
         Tot="20.00"/>
  <Party Contact="Jon Ronson"
         Qty="1"
         Amount="23.00" 
         Tot="23.00"/>
</Parties>

SumConverter:

Imports System.Collections.ObjectModel
Imports System.Reflection

<ValueConversion(GetType(Object()), GetType(String))>
Public Class SumConverter : Implements System.Windows.Data.IMultiValueConverter

    Public Function Convert(ByVal values() As Object, ByVal targetType As System.Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object Implements System.Windows.Data.IMultiValueConverter.Convert
        Static lvItems As IList
        Static lvItem As Xml.XmlElement
        Dim nVal As Double

        Convert = 0
        lvItems = values(0)
        If lvItems Is Nothing Then Exit Function

        For Each lvItem In lvItems
            'Debug.Print(lvItem.GetAttribute("Tot"))
            If Double.TryParse(lvItem.GetAttribute("Tot"), nVal) Then
                Convert = Convert + nVal
            End If
        Next

    End Function

    Public Function ConvertBack(ByVal value As Object, ByVal targetTypes() As System.Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object() Implements System.Windows.Data.IMultiValueConverter.ConvertBack
        ConvertBack = Nothing
    End Function
End Class

Answer 1

Straightforward solution (I’m sure not the best) is to bind a

ElementName = myListView, Path = Items

And in converter traverse items and using VisualTreeHelper.GetChild() find out underlying TextBlock of an item and then int.TryParse(textBlock.Text, out currentItemValue);