c#用Regular Expression查找字符的index

string myText ="33x99 lorem ipsum  004x44";

//the first matched group index

int firstIndex =Regex.Match(myText,"([0-9]+)(x)([0-9]+)").Index;

//first matched "x" (group = 2) index

int firstXIndex =Regex.Match(myText,"([0-9]+)(x)([0-9]+)").Groups[2].Index;