Question

in my project i write tow method to encrypt and decrypt string some string in my xml file
but know i want to encrypt a whole xml file

i want to edit methods to encrypt and decrypt a whole file Instead of string

  public static string Encrypt(string plainText)
          {
                byte[] initVectorBytes = Encoding.ASCII.GetBytes("teto1620@#$%asdf");
                byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
                byte[] keyBytes = Encoding.Unicode.GetBytes("_+)&qwer9512popo");
                RijndaelManaged symmetricKey = new RijndaelManaged();
                symmetricKey.Mode = CipherMode.CBC;
                ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes);
                MemoryStream memoryStream = new MemoryStream();
                CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);
                cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                cryptoStream.FlushFinalBlock();
                byte[] cipherTextBytes = memoryStream.ToArray();
                memoryStream.Close();
                cryptoStream.Close();
                string cipherText = Convert.ToBase64String(cipherTextBytes);
                return cipherText;
          }
          public static string Decrypt(string cipherText)
          {
                byte[] initVectorBytes = Encoding.ASCII.GetBytes("teto1620@#$%asdf");
                byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
                byte[] keyBytes = Encoding.Unicode.GetBytes("_+)&qwer9512popo");
                RijndaelManaged symmetricKey = new RijndaelManaged();
                symmetricKey.Mode = CipherMode.CBC;
                ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes);
                MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
                CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
                byte[] plainTextBytes = new byte[cipherTextBytes.Length];
                int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
                memoryStream.Close();
                cryptoStream.Close();
                string plainText = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
                return plainText;
          }

Answer 1

File.ReadAllText() returns a string so you can just ReadAllText() encrypt using your normal string method, and then use File.WriteAllText() to write the encrypted version back to file.

For large files however, you can read and process line by line instead. e.g.

using (StreamReader sr = new StreamReader("xmlfile.txt")) 
{
    string line;
    while ((line = sr.ReadLine()) != null) 
    {
         File.WriteAllText("mynewxmfile.xml", MyEncryptMethod(line));
    }
}