Extract two substrings from a string

Question

what is the best and optimise wayto extract substrings from a specified string.

my primary string is like

string str = \"ACK

        

Answer 1

string str = @"<ABCMSG><t>ACK</t><t>AAA0</t><t>BBBB1</t></ABCMSG>";
var matches = Regex.Matches(str, @"<t>(\w+)<\/t>");

Console.WriteLine(matches[1].Groups[1]);    // outputs "AAAA1"
Console.WriteLine(matches[2].Groups[1]);    // outputs "BBB2"

This assumes that your data are always inside a <t></t> tag, also you might want to do some error catching in case no matches are found.