Question

Usually i just use a dictionay for key value pairs but I am expectig three columns.

then I need to compare the search term to see if it matches any value in the second column.

Answer 1

class YourDatum 
{
  int Id { get; set; }
  string Value1  { get; set; }
  string Value2 { get; set; }

  public bool Match(string term)
  {
      return Value2.ToUpperInvariant() == term.ToUpperInvariant();
  }
}

var cachedResults = new Dictionary<int, YourDatum>();

//your database calls go here
foreach (var dbRow in dbRows) 
{
   cachedResults.Add(
      idFromDb, 
      new YourDatum {Id=idFromDb, Value1=valueFromDb1, Value2=valueFromDb2});
}

//find a match in the results later on...
string searchTerm = "abcdef";
List<YourDatum> matches= 
    (from datum in cachedResults where 
    datum.Match(searchTerm) select datum).ToList();