// this the ancient method of filtering a collection :D
public List<int> GetValuesGreaterThan100(List<int> masterCollection)
{
            List<int> tempResult = new List<int>();
 
            foreach (var value in masterCollection)
            {
                if (value > 100)
                    tempResult.Add(value);
            }
            return tempResult;
}

// the following snippet is what recommended 
public IEnumerable<int> GetValuesGreaterThan100(List<int> masterCollection)
{
      foreach (var value in masterCollection)
      {
         if (value > 100)
            yield return value;
      }
}