string s = "某某的面积是12345678平方米";
string t = Regex.Replace(s, @"(?<=\d)(?=(\d\d\d)+(?!\d))", ",");
Console.WriteLine(t); //输出:某某的面积是12,345,678平方米转换为Delphiprocedure TForm3.btnPostClick(Sender: TObject);
var
reg: TPerlRegEx;
begin
reg := TPerlRegEx.Create();
reg.Subject := '某某的面积是12345678平方米';
reg.RegEx := '(?<=\d)(?=(\d\d\d)+(?!\d))';
reg.Replacement := ',';
reg.ReplaceAll;
mmoResult.Lines.text:= reg.Subject; //输出结果仍然是 某某的面积是12345678平方米 而不是 某某的面积是12,345,678平方米
end;
reg.Replacement := '\1,';