public string GetPairs()
{
//read last pairs here
FileReadWrite file = new FileReadWrite();
var yesterdayPairs = GetLastPairs(file.ReadFile()); //this returns a List<tuple> of canonical pairs
var todayPairs = new List <Tuple <string, string> >();
var randomPair = _pairs.OrderBy(arg => Guid.NewGuid()).Take(2).ToList();
todayPairs.Add(Tuple.Create(randomPair[0], randomPair[1]));
while (yesterdayPairs.Contains(todayPairs[0]))
{
todayPairs = new List <Tuple <string, string> >();
randomPair = _pairs.OrderBy(arg => Guid.NewGuid()).Take(2).ToList();
todayPairs.Add(Tuple.Create(randomPair[0], randomPair[1]));
}
//then write the new pair
file.WriteToFile($"{todayPairs[0].Item1.ToString()},{todayPairs[0].Item2.ToString()}");
//return the new pair
return($"Today's pairs are : {todayPairs[0].Item1.ToString()} & {todayPairs[0].Item2.ToString()}");
}