byte string convert in C#

    byte[] bStrByte = Encoding.UTF8.GetBytes(str0);   // string -> byte
    string str1 = Encoding.Default.GetString(bStrByte);   // byte -> string

[C#] How to add comma to numbers

int nNum = 123456;  
string strNum = nNum.ToString("#.##0");

Then you will have "123,456".