从字节中读取特殊字符[]

Question

I'm writing and reading from Mifare - RFID cards.

To WRITE into the card, i'm using a Byte[] like this:

byte[] buffer = Encoding.ASCII.GetBytes(txt_IDCard.Text);  

Then, to READ from the card, I'm getting some error with special characters , when it's supposed to show me é, ã, õ, á, à... I get ? instead:

string result = System.Text.Encoding.UTF8.GetString(buffer);
string result2 = System.Text.Encoding.ASCII.GetString(buffer, 0, buffer.Length);
string result3 = Encoding.UTF7.GetString(buffer); 

eg: Instead I get Àgua, amanhã, você I receive/read ?gua, amanh?, voc? .
How may I solve it ?

Answer 1

ASCII by its very definition only supports 128 characters.

What you need is ANSI characters if you are reading legacy text.

You can use Encoding.Default instead of Encoding.ASCII to interpret characters in the current locale's default ANSI code page.

Ideally, you would know exactly which code page you are expecting the ANSI characters to use and specify the code page explicitly using this overload of Encoding.GetEncoding(int codePage) , for example:

string result = System.Text.Encoding.GetEncoding(1252).GetString(buffer);

Here's a very good reference page on Unicode: http://www.joelonsoftware.com/articles/Unicode.html

And another here: http://msdn.microsoft.com/en-us/library/b05tb6tz%28v=vs.90%29.aspx

But maybe you can just use UTF8 when reading and writing

I don't know the details of the card reader. Is the data you read and write to the card just a load of bytes?

If so, you can just use UTF8 for both reading and writing and it will all just work. It's only necessary to use ANSI if you are working with a legacy device which is expecting (or providing) ANSI text. If the device just stores bytes blindly without implying any particular format, you can do what you like - in this case, just always use UTF8.

Answer 2

It seems like you're using characters that aren't mapped in the 7 bits ASCII, but in the "extensions" ISO-8859-1 or ISO-8859-15. You'll need to choose a specific encoding for mapping to your byte array and things should work fine;

byte[] buffer = Encoding.GetEncoding("ISO-8859-1").GetBytes(txt_IDCard.Text);

Answer 3

You have two problems there:

1. ASCII supports only a limited amount of characters.
2. You're currently using two different Encodings for reading and writing.

You should write with the same Encoding as you read.

Writing

    byte[] buffer = Encoding.UTF8.GetBytes(txt_IDCard.Text);  

Reading

    string result = Encoding.UTF8.GetString(buffer);