MultiBinding in Silverlight 5

<UserControl x:Class="SilverlightMarkupExtensions.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:z="clr-namespace:SilverlightMarkupExtensions"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">
    <UserControl.Resources>
        <z:StringFormatMultiValueConverter x:Key="stringFormatConverter" />
        <Style x:Key="myStyle1" TargetType="TextBox">
            <Setter Property="Text" Value="{z:MultiBinding Mode=TwoWay, Source1={Binding Title, Mode=TwoWay}, Converter={StaticResource stringFormatConverter}}" />
            <Setter Property="Tag" Value="{z:MultiBinding Source1={Binding Title}, Converter={StaticResource stringFormatConverter}}" />
        </Style> 
    </UserControl.Resources>
    <Grid x:Name="LayoutRoot" Background="White">
        <Grid.DataContext>
            <z:MyModelView />
        </Grid.DataContext>
        <StackPanel>
            
          <!--  <TextBlock Text="{z:MultiBinding Source1={Binding Title}}" /> 
            <TextBlock Name="title" Text="Title" />
            <TextBlock Text="{z:MultiBinding Source1={Binding Title}}" />  -->
            <TextBlock FontWeight="Bold">MultiBinding in ListBox' ItemsTemplate with StringFormat bound to ComboBox. </TextBlock>
            <StackPanel Orientation="Horizontal" >
                <TextBlock Text="Name format: " />
                <ComboBox Name="cboNameFormat" Width="180" SelectedValuePath="Tag" >
                    <ComboBoxItem Tag="%0 %1" IsSelected="True">First and last name</ComboBoxItem>
                    <ComboBoxItem Tag="%1, %0">Last name, first name</ComboBoxItem>
                </ComboBox>
            </StackPanel>
            <ListBox ItemsSource="{Binding Persons}" >
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <TextBlock>
                            <TextBlock.Text>
                                <z:MultiBinding StringFormat="{Binding SelectedValue, ElementName=cboNameFormat}" >
                                    <z:BindingCollection>
                                        <Binding Path="FirstName" />
                                        <Binding Path="LastName" />
                                    </z:BindingCollection>
                                </z:MultiBinding>
                                </TextBlock.Text>
                        </TextBlock>
                    </DataTemplate>    
                </ListBox.ItemTemplate>    
            </ListBox> 
            <TextBlock FontWeight="Bold">MultiBinding applied via Style</TextBlock>
            <TextBox Style="{StaticResource myStyle1}" /> 
          <!--  <StackPanel DataContext="{x:Null}" >
                <TextBlock  Style="{StaticResource myStyle1}" />
            </StackPanel> -->
            <TextBlock FontWeight="Bold">MultiBinding with bindings to named elements.</TextBlock>
            <CheckBox Name="chkLicenceAccepted" >I have accepted the Licence</CheckBox>
            <CheckBox Name="chkConditionsAccepted" >I have accepted the Conditions</CheckBox>
            <Button Content="Continue" >
                <Button.IsEnabled>
                    <z:MultiBinding Source1="{Binding IsChecked, ElementName=chkLicenceAccepted}" 
                                        Source2="{Binding IsChecked, ElementName=chkConditionsAccepted}" 
                                        Converter="{z:MinNumberOfSetConverter}"
                                        ConverterParameter="2"
                                        />
                </Button.IsEnabled>
            </Button>
            <TextBlock FontWeight="Bold">MultiBinding with two-way binding to two model view properties.</TextBlock>  
            <StackPanel Orientation="Horizontal" >
                <TextBlock Text="Length: " />
                <TextBox Width="100" BindingValidationError="TextBox_BindingValidationError" >
                    <TextBox.Text>
                        <z:MultiBinding Mode="TwoWay" 
                                            NotifyOnValidationError="True" ValidatesOnExceptions="true" 
                                            Converter="{z:LengthConverter}"
                                            Source1="{Binding Length, Mode=TwoWay, ValidatesOnExceptions=true}"
                                            Source2="{Binding LengthUnit, Mode=TwoWay, ValidatesOnExceptions=true}"  />
                    </TextBox.Text>
                </TextBox> 
                <TextBlock Text="{z:MultiBinding Source1={Binding Length},Source2={Binding LengthUnit},StringFormat='%0 %1'}" />
            </StackPanel>
            <TextBlock FontWeight="Bold" >MultiBinding used with a IValueConverter:</TextBlock>
            <TextBox Text="{z:MultiBinding Mode=TwoWay,UpdateSourceTrigger=PropertyChanged, Source1={Binding Title,Mode=TwoWay},Converter={z:ReverseStringConverter}}" />
        </StackPanel>
    </Grid>
</UserControl>