Possible Matchlock Solution

Truple<List<Gem>, bool>  <--What our GetGemsInRow/Col method will return(Truple basically allows us to return two objects from a single method)

the bool will indicate if the list excluded a gem because it was moving, which should indicate that we need to not execute the rest of the FixBoard() method we are currently in- so just call return;

Truple<List<Gem>, bool> trup1 = GetGemsInRow(i, j);
Truple<List<Gem>, bool> trup2 = GetGemsInCol(i, j);

if ((trup1.Item1.Count < 2 && trup2.Item1.Count < 2) || (trup1.Item2 && trup2.Item2))
{
    return;
}