C# windows forms combobox item highlighting

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C#

combobox

I have simple combobox and trying to search items in the dropdown list without filtering. When I upload the text it should highlight the best guess (the one which starts with the letter in the cmbtext etc.). For example there are 'ABC' and 'DEF' when I press A it should just highlight 'ABC'.


How can I achieve this.

What I have tried:

protected override void OnTextUpdate(EventArgs e)
{
    DroppedDown = true;
    searchText = Text;

    SelectedIndex = findIndex(Text);
    Text = searchText; //when dropdown occurs it automatically select an item and writes it in the text place. To prevent this I just update the text
    SelectionStart = Text.Length;
}

private int findIndex(string text)
{
    for (int i = 0; i < dataTable.Rows.Count; i++)
        if (dataTable.Rows[i][1].ToString().ToUpper().StartsWith(text.ToUpper()))
            return i;

    return -1;
}

The code I thought should workd is here. It just blinks the text and then highlight is gone.