string에 헥사값 더하기

string lineOne = "One";
string lineTwo = "Two";
char CarriageReturn = (char)0x0D;
string final = lineOne + CarriageReturn.ToString() + lineTwo + CarriageReturn.ToString();

or the easier to read method:
string lineOne = "One";
string lineTwo = "Two";
string final = string.Format("{0}\r{1}\r", lineOne, lineTwo); // or lineOne + "\r" + lineTwo + "\r";