Encrypt Decrypt string in C# - ASP.Net

public class EncryptDecryptUtil
{
 public static string Decrypt(string strData)
 {
  if (strData.Length > 0)
   return DecodeFrom64(strData);
  else
   return strData;
 }
 public static string Encrypt(string strData)
 {
  if (strData.Length > 0)
   return EncodeBase64(strData);
  else
   return strData;
 }
 internal static string DecodeFrom64(string encodedData)
 {
  try
  {
   byte[] encodedDataAsBytes = System.Convert.FromBase64String(encodedData);
   string returnValue = System.Text.ASCIIEncoding.ASCII.GetString(encodedDataAsBytes);
   return returnValue;
  }
  catch (Exception e)
  {
   throw new Exception("Error in EncodeBase64" + e.Message);
  }
 }
 internal static string EncodeBase64(string data)
 {
  try
  {
   byte[] toencode_byte = System.Text.ASCIIEncoding.ASCII.GetBytes(data);
   string result = Convert.ToBase64String(toencode_byte);
   return result;
  }
  catch (Exception e)
  {
   throw new Exception("Error in EncodeBase64" + e.Message);
  }
 }
}