O'Reilly Book Excerpts: C# Cookbook

Cooking with C#

by Stephen Teilhet and Jay Hilyard

Related Reading C# Cookbook By Stephen Teilhet, Jay Hilyard

Editor's note: Converting strings and handling exceptions, two of the topics covered in depth in today's recipes, are just a few of the hundreds of solutions to specific problems included in C# Cookbook. Whether you're new to the C# language or an experienced C# programmer, C# Cookbook provides practical answers to the day-to-day questions you run up against.

Recipe 2.13: Converting a String Returned as a Byte[ ] Back into a String

Problem

Many methods in the FCL return a byte[] consisting of characters instead of a string. Some of these methods include:

• System.Net.Sockets.Socket.Receive
• System.Net.Sockets.Socket.ReceiveFrom
• System.Net.Sockets.Socket.BeginReceive
• System.Net.Sockets.Socket.BeginReceiveFrom
• System.Net.Sockets.NetworkStream.Read
• System.Net.Sockets.NetworkStream.BeginRead
• System.IO.BinaryReader.Read
• System.IO.BinaryReader.ReadBytes
• System.IO.FileStream.Read
• System.IO.FileStream.BeginRead
• System.IO.MemoryStream // Constructor
• System.IO.MemoryStream.Read
• System.IO.MemoryStream.BeginRead
• System.Security.Cryptography.CryptoStream.Read
• System.Security.Cryptography.CryptoStream.BeginRead
• System.Diagnostics.EventLogEntry.Data

In many cases, this byte[] might contain ASCII or Unicode encoded characters. You need a way to recombine this byte[] to obtain the original string.

Solution

To convert a byte array of ASCII values to a complete string, use the following method:

using System;
using System.Text;

public static string FromASCIIByteArray(byte[] characters)
{
    ASCIIEncoding encoding = new ASCIIEncoding( );
    string constructedString = encoding.GetString(characters);

    return (constructedString);
}

To convert a byte array of Unicode values (UTF-16 encoded) to a complete string, use the following method:

public static string FromUnicodeByteArray(byte[] characters)
{
    UnicodeEncoding encoding = new UnicodeEncoding( );
    string constructedString = encoding.GetString(characters);

    return (constructedString);
}

Discussion

The GetString method of the ASCIIEncoding class converts 7-bit ASCII characters contained in a byte array to a string. Any value larger than 127 will be AND'ed with the value 127 and the resulting character value will be displayed in the string. For example, if the byte array contains the value 200, this value will be converted to 72, and the character equivalent of 72 ('H') will be displayed. The ASCIIEncoding class can be found in the System.Text namespace. The GetString method is overloaded to accept additional arguments as well. The overloaded versions of the method convert all or part of a string to ASCII and then store the result in a specified range inside a byte array.

The GetString method returns a string containing the converted byte array of ASCII characters.

The GetString method of the UnicodeEncoding class converts Unicode characters into 16-bit Unicode values. The UnicodeEncoding class can be found in the System.Text namespace. The GetString method returns a string containing the converted byte array of Unicode characters.

See Also

See the "ASCIIEncoding Class" and "UnicodeEncoding Class" topics in the MSDN documentation.

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