I have a string:
\"Hello 7866592 this is my 12432 string and 823 i need to flip all 123\"
var replacedString =
Regex.Replace(//finds all matches and replaces them
myString, //string we're working with
@"\d+", //the regular expression to match to do a replace
m => new string(m.Value.Reverse().ToArray())); //a Lambda expression which
//is cast to the MatchEvaluator delegate, so once the match is found, it
//is replaced with the output of this method.