<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="FontSizeConverter_Csharp.Window1" Title="FontSizeConverter Sample"> <StackPanel> <TextBlock Name="text1" TextWrapping="Wrap" Height="300" Width="500"> this is a test </TextBlock> <ListBox Grid.Column="1" Grid.Row="1" VerticalAlignment="Top" Height="50" Margin="10,0,0,0" SelectionChanged="changeSize"> <ListBoxItem>5</ListBoxItem> <ListBoxItem>8</ListBoxItem> <ListBoxItem>11</ListBoxItem> <ListBoxItem>14</ListBoxItem> <ListBoxItem>17</ListBoxItem> <ListBoxItem>20</ListBoxItem> <ListBoxItem>23</ListBoxItem> <ListBoxItem>26</ListBoxItem> <ListBoxItem>29</ListBoxItem> <ListBoxItem>32</ListBoxItem> </ListBox> <ListBox Grid.Column="3" Grid.Row="1" VerticalAlignment="Top" Height="50" Margin="10,0,0,0" SelectionChanged="changeFamily"> <ListBoxItem>Arial</ListBoxItem> <ListBoxItem>Courier New</ListBoxItem> <ListBoxItem>Tahoma</ListBoxItem> <ListBoxItem>Times New Roman</ListBoxItem> <ListBoxItem>Verdana</ListBoxItem> </ListBox> </StackPanel> </Window> //File:Window.xaml.cs using System; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Navigation; using System.Windows.Media; namespace FontSizeConverter_Csharp { public partial class Window1 : Window { public void changeSize(object sender, SelectionChangedEventArgs args) { ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem); FontSizeConverter myFontSizeConverter = new FontSizeConverter(); text1.FontSize = (Double)myFontSizeConverter.ConvertFromString(li.Content.ToString()); } public void changeFamily(object sender, SelectionChangedEventArgs args) { ListBoxItem li2 = ((sender as ListBox).SelectedItem as ListBoxItem); text1.FontFamily = new System.Windows.Media.FontFamily(li2.Content.ToString()); } } }