coding for Encoding and Decoding

//encode
string data = "a";
byte[] encData_byte = new byte[data.Length];
encData_byte = System.Text.Encoding.UTF8.GetBytes(data);
string encodedData = Convert.ToBase64String(encData_byte);
Response.Write(encodedData.ToString());

//decode

System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();
System.Text.Decoder utf8Decode = encoder.GetDecoder();

byte[] todecode_byte = Convert.FromBase64String(encodedData.ToString());
int charCount = utf8Decode.GetCharCount(todecode_byte, 0, todecode_byte.Length);
char[] decoded_char = new char[charCount];
utf8Decode.GetChars(todecode_byte, 0, todecode_byte.Length, decoded_char, 0);
string result = new String(decoded_char);
Response.Write(result.ToString());