How to Write BUFFER & Read TEXT with Encrypt file ?

Question

I'm using Windows Phone 8.1 RT.
I have a issue :
- I write a BUFFER encrypted to file. After, I read file with TEXT. It's throw exception : No mapping for the Unicode character exists in the target multi-byte code page. (//ERROR 2)
- I write a TEXT encrypted to file. After, I read file with BUFFER. It's throw exception : The supplied user buffer is not valid for the requested operation. (//ERROR 1)
Code Write Buffer & Read Text.
//Write Textstring msg = EncryptText.Text;
//ERROR 1 - Use 1 or 2
await WriteTextAsync(this.file, msg);
//ERROR 1
//Read Buffer
string msg;
//ERROR 1 - Use 1 or 2
IBuffer buffer = await ReadBufferAsync(this.file);
StreamReader stream = new StreamReader(buffer.AsStream());
msg = stream.ReadToEnd();
//ERROR 1
Code Encrypt-Decypt.
public static string EncryptString(string msg)
            var bufferMsg = CryptographicBuffer.ConvertStringToBinary(msg, BinaryStringEncoding.Utf8);
            var bufferMsgEncrypted = Encrypt(bufferMsg);
            var msgEncrypted = CryptographicBuffer.EncodeToBase64String(bufferMsgEncrypted);
            return msgEncrypted;
        }public static IAsyncAction WriteTextAsync(IStorageFile file, string msg)
            return FileIO.WriteTextAsync(file, EncryptString(msg));
public static IBuffer Decrypt(IBuffer bufferMsg)
            var key = CreateKey(KEY);
            var aes = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.AesCbcPkcs7);
            var symetricKey = aes.CreateSymmetricKey(key);
            var bufferMsgDecrypted = CryptographicEngine.Decrypt(symetricKey, bufferMsg, null);
            return bufferMsgDecrypted;
        }public static IAsyncOperation<IBuffer> ReadBufferAsync(IStorageFile file)
            var buffer = FileIO.ReadBufferAsync(file);
            Task<IBuffer> result = Task.Run<IBuffer>(async () =>
                var Buffer = await buffer;
                return Decrypt(Buffer);
            return result.AsAsyncOperation();
Link demo code :
https://drive.google.com/file/d/0B_cS3IYO936_akE0cmI4bExJMjh0RU9qR3RvWDBWWElZWC1z/view?usp=sharing

Answer 1

Please provide a working app so this can be tested. You can upload to OneDrive and share a link here.
Matt Small - Microsoft Escalation Engineer - Forum Moderator
If my reply answers your question, please mark this post as answered.
NOTE: If I ask for code, please provide something that I can drop directly into a project and run (including XAML), or an actual application project. I'm trying to help a lot of people, so I don't have time to figure out weird snippets with undefined
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