This will give you exactly the strings that you asked for:
string s = "String goes here";
string lineAlignedRight = String.Format("{0,27}", s);
string lineAlignedCenter = String.Format("{0,-27}",
String.Format("{0," + ((27 + s.Length) / 2).ToString() + "}", s));
string lineAlignedLeft = String.Format("{0,-27}", s);