Dynamic TabControl - TabItems

What we want to achieve is to dynamically insert TabItems, with dynamic header.
Plus at any one time, there may only be one TabItem, so we need to check if the tabControl contains the tabItem before creating.

MainWindow.xaml

<Window x:Class="HomeWork.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:HomeWork.UserControls"
        Title="MainWindow" 
        Height="350" 
        Width="525">
    <DockPanel>
        
        <ListBox DockPanel.Dock="Left" Margin="5" MinWidth="120">
            <ListBoxItem x:Name="A1" Content="A1" MouseDoubleClick="NewTabItem" />
            <ListBoxItem x:Name="A2" Content="A2" MouseDoubleClick="NewTabItem" />
        </ListBox>

        <TabControl x:Name="placeholder" Margin="5">            
        </TabControl>        
      
    </DockPanel>
</Window>

MainWindow.cs

public void NewTabItem(object sender, RoutedEventArgs e)
{
  ListBoxItem source = sender as ListBoxItem;
  if (source != null)
  {
    bool tabExists = false;
    foreach (var tabItem in this.placeholder.Items)
    {
       if ((tabItem as TabItem).Name == source.Name)
       {
         tabExists = true;
        }
     }
     if (tabExists == false)
     {
       this.placeholder.SelectedIndex =
           this.placeholder.Items.Add(new TabItem 
               { Header = source.Name, Name = source.Name });
     }
   }
}