Windows Forms. ComboBox Text after DropDown

Hello.

I have ComboBox, which DataSource is DataView, filtered by ComboBox' Text (filter is done in _KeyUp event). How can I change ComboBox that it would not rewrite Text after DropDown and that it would choose the first item in the dropped list?

Example what happens:
0. There are Rows in DataView which has no filter:
    12345
    12435
    31248
    49841

1. Type "3" into ComboBox' Text
2. DataView Rows are filtered into
    12345
    12435
    31248

3. Execute DropDown, and
3.1. Selected item in the list is 31248;
3.2. Text is changed to 31248.

I need that selected item should be 12345 or nothing, and Text is like it was before, 3.

Help, please.

Sincerely,
Daumast