オートコンプリート ボックスをオブジェクトにバインドできます。
class MyClass
{
public int Organization_ID{ get; set; }
public string Organization_Names{ get; set; }
}
<controls:AutoCompleteBox x:Name="autoCompleteBox1"
SelectionChanged="autoCompleteBox1_SelectionChanged"
FilterMode="Contains"
IsTextCompletionEnabled="True">
<controls:AutoCompleteBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Organization_Names}" />
</DataTemplate>
</controls:AutoCompleteBox.ItemTemplate>
</controls:AutoCompleteBox>
private void autoCompleteBox1_SelectionChanged(object sender, RoutedEventArgs e)
{
MessageBox.Show(((MyClass)autoCompleteBox1.SelectedItem).Organization_ID);
}