You can use the following code for conversion between string and byte array.
string s = "Hello World";
// String to Byte[]
byte[] byte1 = System.Text.Encoding.Default.GetBytes(s);
// OR
byte[] byte2 = System.Text.ASCIIEncoding.Default.GetBytes(s);
// Byte[] to string
string str = System.Text.Encoding.UTF8.GetString(byte1);