ComboBoxItem represent an item in a ComboBox.
Example:
XAML
<Window x:Class="WpfApplication3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ComboBox x:Name="cbo"
HorizontalAlignment="Left" VerticalAlignment="Top" Width="120" SelectionChanged="ComboBox_SelectionChanged">
<ComboBoxItem>Option1</ComboBoxItem>
<ComboBoxItem>Option2</ComboBoxItem>
</ComboBox>
</Grid>
</Window>
C#
private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
string value = ((ComboBoxItem)cbo.SelectedItem).Content.ToString();
}