string line="XXX YY ZZ";

string line="XX  YY ZZ";

string[] allId = line.Split(' ');

var allId = line.Split(new char[] {' '}, StringSplitOptions.RemoveEmptyEntries);

var result = Regex.Split("XX  YYY    ZZZ", @"s+");

// "XX", "YYY", "ZZZ" returned in array

string[] allId = line.Split(new char[] {' '}, StringSplitOptions.RemoveEmptyEntries);