Nrthugu

I have a listView of items which are 'Book' instances, and when I click on a book the combobox should display its keywords; in fact it's a little trickier : the combobox contains the list of all the keywords of all books (duplicates removed)(the comboboxItems are checkboxes), and those of the selected book are checked.
here is the multibinding:

<ComboBox

                        x:Name="cbb_Keywords"

                        Grid.Column="2"

                        Width="300"

                        Margin="5,0,0,0"

                        HorizontalAlignment="Left"

                        ItemsSource="{Binding Source={StaticResource AllBooks}}"

                        DataContext="{Binding ElementName=listBoxBooks,Path=SelectedItem,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">



                        <ComboBox.ItemTemplate>

                            <DataTemplate>

                                <StackPanel Orientation="Horizontal">

                                    <CheckBox Width="200">

                                        <CheckBox.IsChecked>

                                            <MultiBinding Converter="{StaticResource TextInListTrueFalseConverter}" >

                                                <Binding Path="KeywordsForTextbox"></Binding>

                                                <Binding RelativeSource="{RelativeSource Self}" Path="Content"></Binding>

                                            </MultiBinding>

                                        </CheckBox.IsChecked>

                                    </CheckBox>

                                </StackPanel>

                            </DataTemplate>

                        </ComboBox.ItemTemplate>

                    </ComboBox>

When I run my program, is seems ok when I click on a book, but I get an exception when I click on the combobox : impossible cast from 'MS.Internal.NamedObject' to 'System.String' type. I saw that value[0] is UnsetValue.

At debugging, when I use spies to track the value of WpfApp1.App.Books[0].KeywordsForTextbox, it gives me the good value (a string which is the list of the keywords of Book[0]. maybe the problem comes from listboxBooks.SelectedItem.KeywordsForTextBox? I can't spy in VS the value of 'listboxBooks'.

some related content...
the beginning of the constructor of MainWindow:

public MainWindow()

        {





            InitializeComponent();

            listBoxBooks.ItemsSource = App.Books;

the convert method of the converter:

public object Convert(object values, Type targetType, object parameter, CultureInfo culture)

        {

            var check = false;

            if ((values != null && values.Length == 2))

            {

                string listString = (string)values[0];

                string wordToFind = (string) values[1];

                if ((listString != null))

                {

                    List<string> keywordsList = listString.Split(',').ToList();

                    if (keywordsList.Contains(wordToFind)) check = true;

                }



            }



            return check;





        }

the KeywordsForTextbox method:

public string KeywordsForTextbox

        {

            get { return string.Join(",", _keywords); }



        }

and finally the implementation of AllBooks:(as a window resource)

<ObjectDataProvider

            x:Key="AllBooks"

            MethodName="listOfAllKeywords"

            ObjectType="{x:Type mangmt:BookManagement}" />

thank you.

The first Binding of the Multi should be to be to the SelectedItem in the ListBox of Books. I have added in the <CheckBox.IsChecked> where appropriate, and Content="{Binding}" to the CheckBox:

                <ComboBox.ItemTemplate>

                    <DataTemplate>

                        <StackPanel Orientation="Horizontal">

                            <CheckBox Width="200" Content={Binding}>

                              <CheckBox.IsChecked>

                                <MultiBinding Converter="{StaticResource TextInListTrueFalseConverter}" >

                                    <Binding ElementName=listBoxBooks, Path=SelectedItem.KeywordsForTextbox"></Binding>

                                    <Binding RelativeSource="{RelativeSource Self}" Path="Content"></Binding>

                                </MultiBinding>

                              </CheckBox.IsChecked>

                            </CheckBox>

                        </StackPanel>

                    </DataTemplate>

                </ComboBox.ItemTemplate>

You may also wish to add some validation to the IMultiValueConverter to make sure the passed values are not unset, to avoid an exception: If Not values(0) Is DependencyProperty.UnsetValue And Not values(1) Is DependencyProperty.UnsetValue Then in VB.

Regarding the behaviour on checking the checkbox, I am guessing this is because of the ConvertBack Method of the IMultiValueConverter. You can remove the 'Throw Exception' code, and write a method to add/remove the text of the checked/unchecked box to your keyword list.