I am creating a WPF app containing a ComboBox which shows some data. I want to use the combobox-integrated text seach. But the problem is, if the user searchs for "llo", the list should show all items, containing this text snippet, like "Hallo", "Hello", "Rollo" ... But the search returns no result because the property name of no item starts with "llo". Has somebody an idea how to achieve this?

I am using the MVVM-pattern. The view is binded to a collection of DTOs (property of the viewmodel), in the DTO there are two properties which are relevant for the search. 

```xml
        <ComboBox 
            ItemsSource="{Binding Path=Agencies}"
            SelectedItem="{Binding Path=SelectedAgency}"
            IsTextSearchEnabled="True"
            DisplayMemberPath="ComboText"
            IsEnabled="{Binding IsReady}"
            IsEditable="True"
            Grid.Column="0"
            Grid.Row="0" 
            IsTextSearchCaseSensitive="False"
            HorizontalAlignment="Stretch">
        </ComboBox>

```

```cs

    public class Agency
    {
        public int AgencyNumber { get; set; }
        public string Title { get; set; }
        public string Name { get; set; }
        public string ContactPerson { get; set; }
        public string ComboText => $"{this.AgencyNumber}\t{this.Name}";
    }

```