Can't read from MemoryStream from current position

 //1. retrieve the encrypted key and the encrypted iv from the cipher
            MemoryStream input = new MemoryStream(cipher);

            //1a
            byte[] encryptedKey = new byte[128]; //note about 128, get the proper size of the encrytped key after manually debugging the hybridecrypt
            input.Read(encryptedKey, 0, encryptedKey.Length);

            //1b do the same thing for the iv
            byte[] encryptedIV = new byte[128];
            input.Read(encryptedIV, 0 , encryptedIV.Length);

            //2. read the left data i.e. the encrypted file data (cipher.Length - encryptedkey.length - encrtypediv.length)
            //it continues reading the remaining bytes therefore if the enc key and enc iv were 128 bytes each, it means that ToArray will continue reading from position 256 till end of file
            byte[] originalFileCipher = input.ToArray();

            //3. decrypt asymmetrically using the private key the enc key and enc iv
            byte[] decryptedKey = AsymmetricDecrypt(encryptedKey, privateKey);
            byte[] decryptedIV = AsymmetricDecrypt(encryptedIV, privateKey);

            //4. decrypt symmetrically the originalFileCipherNotIncludingTheSymmKeys using the decrypted key and decrypted iv
            byte[] originalBytes = SymmetricDecrypt(originalFileCipher, decryptedKey, decryptedIV);

 //1. retrieve the encrypted key and the encrypted iv from the cipher
            MemoryStream input = new MemoryStream(cipher);

            //1a
            byte[] encryptedKey = new byte[128]; //note about 128, get the proper size of the encrytped key after manually debugging the hybridecrypt
            input.Read(encryptedKey, 0, encryptedKey.Length);

            //1b do the same thing for the iv
            byte[] encryptedIV = new byte[128];
            input.Read(encryptedIV, 0 , encryptedIV.Length);

            //2. read the left data i.e. the encrypted file data (cipher.Length - encryptedkey.length - encrtypediv.length)
            //it continues reading the remaining bytes therefore if the enc key and enc iv were 128 bytes each, it means that ToArray will continue reading from position 256 till end of file
            byte[] originalFileCipher = input.ToArray();

            //3. decrypt asymmetrically using the private key the enc key and enc iv
            byte[] decryptedKey = AsymmetricDecrypt(encryptedKey, privateKey);
            byte[] decryptedIV = AsymmetricDecrypt(encryptedIV, privateKey);

            //4. decrypt symmetrically the originalFileCipherNotIncludingTheSymmKeys using the decrypted key and decrypted iv
            byte[] originalBytes = SymmetricDecrypt(originalFileCipher, decryptedKey, decryptedIV);

byte[] originalFileCipher = new byte[length];

byte[] originalFileCipher = new byte[length];