string a = "34-1/+2";
Match match = Regex.Match(a, @"(\d*)(-\d+)/(\+?\d+)");
if (match.Groups[1].Value == string.Empty)
Console.WriteLine($"{int.Parse(match.Groups[2].Value)}, {int.Parse(match.Groups[3].Value)}");
else
Console.WriteLine($"{int.Parse(match.Groups[1].Value) + int.Parse(match.Groups[2].Value)}, {int.Parse(match.Groups[1].Value) + int.Parse(match.Groups[3].Value)}");
试试看吧