String Encoding/Decoding and Conversions in C#

This article has been excerpted from book "The Complete Visual C# Programmer's Guide" from the Authors of C# Corner.

All strings in a .NET Framework program are stored as 16-bit Unicode characters. At times you might need to convert from Unicode to some other character encoding, or from some other character encoding to Unicode. The .NET Framework provides several classes for encoding (converting Unicode characters to a block of bytes in another encoding) and decoding (converting a block of bytes in another encoding to Unicode characters. 

The System.Text namespace has a number of Encoding implementations:

• The ASCIIEncoding class encodes Unicode characters as single 7-bit ASCII characters. This class supports only character values between U+0000 and U+007F.
• The UnicodeEncoding class encodes each Unicode character as two consecutive bytes. This supports both little-endian (code page 1200) and big-endian (code page 1201) byte orders.
• The UTF7Encoding class encodes Unicode characters using UTF-7 encoding (UTF-7 stands for UCS Transformation Format, 8-bit form). This supports all Unicode character values and can also be accessed as code page 65000.
• The UTF8Encoding class encodes Unicode characters using UTF-8 encoding (UTF-8 stands for UCS Transformation Format, 8-bit form). This supports all Unicode character values and can also be accessed as code page 65001.

Each of these classes has methods for both encoding (such as GetBytes) and decoding (such as GetChars) a single array all at once. In addition, each supports GetEncoder and GetDecoder, which return encoders and decoders capable of maintaining shift state so they can be used with streams and blocks. 

Listing 20.33 shows various forms of the Encoding class. 

Listing 20.33: Encoding and Decoding 

             // writing

            FileStream fs = new FileStream("text.txt", FileMode.OpenOrCreate);

            StreamWriter t = new StreamWriter(fs, Encoding.UTF8);

            t.Write("This is in UTF8");

            //or

            // reading

            FileStream fs = new FileStream("text.txt", FileMode.Open);

            StreamReader t = new StreamReader(fs, Encoding.UTF8);

            String s = t.ReadLine();

Listing 20.34 makes a Web page request and then encodes the bytes returned/read as ASCII characters. 

Listing 20.34: String Encoding 

// encoding example

using System;

using System.Net;

using System.IO;

using System.Text;

class MyApp

{

    static void Main()

    {

        try

        {

            WebRequest theRequest =

            WebRequest.Create(@"http://www.mindcracker.com");

            WebResponse theResponse = theRequest.GetResponse();

            int BytesRead = 0;

            Byte[] Buffer = new Byte[256];// Buffer Size

            Stream ResponseStream = theResponse.GetResponseStream();

            BytesRead = ResponseStream.Read(Buffer, 0, 256);

            StringBuilder strResponse = new StringBuilder(@"");

            while (BytesRead != 0)

            {

                // Returns an encoding for the ASCII (7 bit) character set

                // ASCII characters are limited to the lowest 128 Unicode

                // characters

                // , from U+0000 to U+007f.

                strResponse.Append(Encoding.ASCII.GetString(Buffer,

                0, BytesRead));

                BytesRead = ResponseStream.Read(Buffer, 0, 256);

            }

            Console.Write(strResponse.ToString());

        }

        catch (Exception e)

        {

            Console.Write("Exception Occured!{0}", e.ToString());

        }

    }

}

Conclusion

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The Complete Visual C# Programmer's Guide covers most of the major components that make up C# and the .net environment. The book is geared toward the intermediate programmer, but contains enough material to satisfy the advanced developer.