You can so domething like this :
private readonly List<string> items = new List<string> { "first One ", "second term", "extra one" };
private BindingList<string> _bindinglist;
In Form_Load :
_bindinglist = new BindingList<string>(items);
comboBox1.DataSource = _bindinglist;
Test in a Button click
string sKey = "One";
Console.WriteLine(sKey);
var newList = _bindinglist.Where(c => c.IndexOf(sKey, StringComparison.OrdinalIgnoreCase) >= 0);
foreach (var sItem in newList)
{
Console.WriteLine("\t" + sItem);
}
sKey = "second";
Console.WriteLine(sKey);
newList = _bindinglist.Where(c => c.IndexOf(sKey, StringComparison.OrdinalIgnoreCase) >= 0);
foreach (var sItem in newList)
{
Console.WriteLine("\t" + sItem);
}