How to decrypt a string in C # was encrypted in iOS using Rijndael

I am trying to encrypt and decrypt a string using object c and c #. both work fine in native code, but when I tried to decrypt the string in C # it was encrypted in iOS. I am getting some error.

This was the code I used in object c

- (NSData *)AES256EncryptWithKey:(NSString *)key  Data: (NSData *) data
{
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)

    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)

    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [data length];

    NSData *iv =  [@"abcdefghijklmnopqrstuvwxyz123456" dataUsingEncoding:NSUTF8StringEncoding];

    size_t bufferSize = dataLength + kCCBlockSizeAES128;

    void *buffer = malloc(bufferSize);

    size_t numBytesEncrypted = 0;

    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          [iv bytes] /* initialization vector (optional) */,
                                          [data bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesEncrypted);

    if (cryptStatus == kCCSuccess)
    {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }

    free(buffer); //free the buffer;

    return nil;
}

      

        
        
        
      

    

To find out how to decrypt in C # I give blockize 256, ivsize to 32 and use "RijndaelManaged ()". I am not using salt and password. Error: Something like "Cancellation is invalid and cannot be removed." I tried to install the add-on as well as PKCS7, but no, but nothing helps to decrypt.

can anyone help?

Edit: My C # code is here

public string DecryptString(string encrypted)
{
    string result = null;
    _encoder = new UTF8Encoding();
    if (!string.IsNullOrWhiteSpace(encrypted) && (encrypted.Length >= 32))
    {
        var messageBytes = Convert.FromBase64String(encrypted);
        using (var rm = new RijndaelManaged())
        { 
            rm.BlockSize = _blockSize;
            rm.Key = _encoder.GetBytes("mykey_here");
            rm.IV = _encoder.GetBytes("abcdefghijklmnopqrstuvwxyz123456"); ;
            rm.Padding = PaddingMode.Zeros;
            var decryptor = rm.CreateDecryptor(rm.Key, messageBytes.Take(_ivSize).ToArray());
            result = _encoder.GetString(Transform(messageBytes.Skip(_ivSize).ToArray(), decryptor));
        }
    }

    return result;
}

protected byte[] Transform(byte[] buffer, ICryptoTransform transform)
{
    byte[] result;
    using (var stream = new MemoryStream())
    using (var cs = new CryptoStream(stream, transform, CryptoStreamMode.Write))
    {
        cs.Write(buffer, 0, buffer.Length);
        cs.FlushFinalBlock();
        result = stream.ToArray();
    }

    return result;
}