AutoCompleteBox with TextChanged event not selecting properly - silverlight

Question

Hi I'm using an AutoCompleteBox like this
<!-- XAML Code -->
<sdk:AutoCompleteBox Grid.Row="2"
FilterMode="None"
ItemsSource="{Binding Customers}"
SelectedItem="{Binding Path=SelectedCustomer, Mode=TwoWay}"
Text="{Binding CustomerSearchString, Mode=TwoWay}"
ValueMemberBinding="{Binding Path=FullName}"
ValueMemberPath="FullName"
TextChanged="{ext:Invoke MethodName=Search, Source={Binding}}"/>
C# part:
// Search Method in the viewmodel
public void Search()
{
var customerOperation = _context.Load(_context.GetCustomerByNameQuery(CustomerSearchString));
customerOperation.Completed += (s, e) => Customers = new List<Customer>(customerOperation.Entities);
}
In my app to quick-search for customers for an fast and uncomplicated method to search. I get it to display everything correctly in the dropdown, and when I select with the mouse it works perfectly.
But when I press ArrowDown, you see the text come up for a split-second but then it reverts and puts the cursor back in the textbox instead of selecting the first entry down. I tried using the TextInput event, but that one won't fire.
How can I avoid this behaviour?
SOLUTION:
The problem was, that the TextChanged event got fired when the user selected an entry, creating some sort of race condition like behaviour where the Text got reset. The solution was to use the KeyUp event (don't use KeyDown, because the Text property won't be updated yet). This event doesn't get triggered when the user selects something, solving the problem.
Final code (ViewModel unchanged):
<!-- XAML Code -->
<sdk:AutoCompleteBox Grid.Row="2"
FilterMode="None"
ItemsSource="{Binding Customers}"
SelectedItem="{Binding Path=SelectedCustomer, Mode=TwoWay}"
Text="{Binding CustomerSearchString, Mode=TwoWay}"
ValueMemberBinding="{Binding Path=FullName}"
ValueMemberPath="FullName"
KeyUp="{ext:Invoke MethodName=Search, Source={Binding}}"/>
Thanks everyone!

Answer 1

Add a handler like this in code:
KeyEventHandler eventHandler = MyAutoCompleteBox_KeyDown;
MyAutoCompleteBox.AddHandler(KeyDownEvent, eventHandler, true);

Answer 2

I'm not understanding why you are using a TextChanged event...? What is that for? If you take that out, does it work? I use an autocomplete box in my project and I don't need a search method... all I do is just supply a list of objects to the autocompletebox and the it searches that list when the user types. I can select either by mouse or by up/down arrows. The only thing that I can think of is that each time you try to use the up/down arrow the text changes and fires off the search function and closes the selection option drop down...