Byte Structure

You can instantiate a Byte value in several ways:

• You can declare a Byte variable and assign it a literal integer value that is within the range of the Byte data type. The following example declares two Byte variables and assigns them values in this way.

  C#

  VB

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  byte value1 = 64;
  byte value2 = 255;
  
  
  

• You can assign a non-byte numeric value to a byte. This is a narrowing conversion, so it requires a cast operator in C# and a conversion method in Visual Basic if Option Strict is on. If the non-byte value is a Single, Double, or Decimal value that includes a fractional component, the handling of its fractional part depends on the compiler performing the conversion. The following example assigns several numeric values to Byte variables.

  C#

  VB

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  int int1 = 128;
  try {
     byte value1 = (byte) int1;
     Console.WriteLine(value1);
  }
  catch (OverflowException) {
     Console.WriteLine("{0} is out of range of a byte.", int1);
  }
  
  double dbl2 = 3.997;
  try {
     byte value2 = (byte) dbl2;
     Console.WriteLine(value2);
  }
  catch (OverflowException) {
     Console.WriteLine("{0} is out of range of a byte.", dbl2);
  }
  // The example displays the following output:
  //       128
  //       4      
  
  
  

• You can call a method of the Convert class to convert any supported type to a Byte value. This is possible because Byte supports the IConvertible interface. The following example illustrates the conversion of an array of Int32 values to Byte values.

  C#

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  int[] numbers = { Int32.MinValue, -1, 0, 121, 340, Int32.MaxValue };
  byte result;
  foreach (int number in numbers)
  {
     try {
        result = Convert.ToByte(number);
        Console.WriteLine("Converted the {0} value {1} to the {2} value {3}.", 
                          number.GetType().Name, number, 
                          result.GetType().Name, result);
     }                     
     catch (OverflowException) {
        Console.WriteLine("The {0} value {1} is outside the range of the Byte type.", 
                          number.GetType().Name, number);
     }
  }
  // The example displays the following output:
  //       The Int32 value -2147483648 is outside the range of the Byte type.
  //       The Int32 value -1 is outside the range of the Byte type.
  //       Converted the Int32 value 0 to the Byte value 0.
  //       Converted the Int32 value 121 to the Byte value 121.
  //       The Int32 value 340 is outside the range of the Byte type.
  //       The Int32 value 2147483647 is outside the range of the Byte type.      
  
  
  

• You can call the Parse or TryParse method to convert the string representation of a Byte value to a Byte. The string can contain either decimal or hexadecimal digits. The following example illustrates the parse operation by using both a decimal and a hexadecimal string.

  C#

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  string string1 = "244";
  try {
     byte byte1 = Byte.Parse(string1);
     Console.WriteLine(byte1);
  }
  catch (OverflowException) {
     Console.WriteLine("'{0}' is out of range of a byte.", string1);
  }
  catch (FormatException) {
     Console.WriteLine("'{0}' is out of range of a byte.", string1);
  }
  
  string string2 = "F9";
  try {
     byte byte2 = Byte.Parse(string2, 
                             System.Globalization.NumberStyles.HexNumber);
     Console.WriteLine(byte2);
  }
  catch (OverflowException) {
     Console.WriteLine("'{0}' is out of range of a byte.", string2);
  }
  catch (FormatException) {
     Console.WriteLine("'{0}' is out of range of a byte.", string2);
  }
  // The example displays the following output:
  //       244
  //       249
  
  
  

The Byte type supports standard mathematical operations such as addition, subtraction, division, multiplication, subtraction, negation, and unary negation. Like the other integral types, the Byte type also supports the bitwise AND, OR, XOR, left shift, and right shift operators.

You can use the standard numeric operators to compare two Byte values, or you can call the CompareTo or Equals method.

The Byte type provides full support for standard and custom numeric format strings. (For more information, see Formatting Types, Standard Numeric Format Strings, and Custom Numeric Format Strings.) However, most commonly, byte values are represented as one-digit to three-digit values without any additional formatting, or as two-digit hexadecimal values.

To format a Byte value as an integral string with no leading zeros, you can call the parameterless ToString() method. By using the "D" format specifier, you can also include a specified number of leading zeros in the string representation. By using the "X" format specifier, you can represent a Byte value as a hexadecimal string. The following example formats the elements in an array of Byte values in these three ways.

byte[] numbers = { 0, 16, 104, 213 };
foreach (byte number in numbers) {
   // Display value using default formatting.
   Console.Write("{0,-3}  -->   ", number.ToString());
   // Display value with 3 digits and leading zeros.
   Console.Write(number.ToString("D3") + "   ");
   // Display value with hexadecimal.
   Console.Write(number.ToString("X2") + "   ");
   // Display value with four hexadecimal digits.
   Console.WriteLine(number.ToString("X4"));
}   
// The example displays the following output:
//       0    -->   000   00   0000
//       16   -->   016   10   0010
//       104  -->   104   68   0068
//       213  -->   213   D5   00D5      

You can also format a Byte value as a binary, octal, decimal, or hexadecimal string by calling the ToString(Byte, Int32) method and supplying the base as the method's second parameter. The following example calls this method to display the binary, octal, and hexadecimal representations of an array of byte values.

byte[] numbers ={ 0, 16, 104, 213 };
Console.WriteLine("{0}   {1,8}   {2,5}   {3,5}",
                  "Value", "Binary", "Octal", "Hex");
foreach (byte number in numbers) {
   Console.WriteLine("{0,5}   {1,8}   {2,5}   {3,5}",
                     number, Convert.ToString(number, 2),
                     Convert.ToString(number, 8),
                     Convert.ToString(number, 16));
}      
// The example displays the following output:
//       Value     Binary   Octal     Hex
//           0          0       0       0
//          16      10000      20      10
//         104    1101000     150      68
//         213   11010101     325      d5      

In addition to working with individual bytes as decimal values, you may want to perform bitwise operations with byte values, or work with byte arrays or with the binary or hexadecimal representations of byte values. For example, overloads of the BitConverter.GetBytes method can convert each of the primitive data types to a byte array, and the BigInteger.ToByteArray method converts a BigInteger value to a byte array.

Byte values are represented in 8 bits by their magnitude only, without a sign bit. This is important to keep in mind when you perform bitwise operations on Byte values or when you work with individual bits. In order to perform a numeric, Boolean, or comparison operation on any two non-decimal values, both values must use the same representation.

When an operation is performed on two Byte values, the values share the same representation, so the result is accurate. This is illustrated in the following example, which masks the lowest-order bit of a Byte value to ensure that it is even.

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      string[] values = { Convert.ToString(12, 16), 
                          Convert.ToString(123, 16), 
                          Convert.ToString(245, 16) };

      byte mask = 0xFE;
      foreach (string value in values) {
         Byte byteValue = Byte.Parse(value, NumberStyles.AllowHexSpecifier);
         Console.WriteLine("{0} And {1} = {2}", byteValue, mask,  
                           byteValue & mask);
      }
   }
}
// The example displays the following output:
//       12 And 254 = 12
//       123 And 254 = 122
//       245 And 254 = 244

On the other hand, when you work with both unsigned and signed bits, bitwise operations are complicated by the fact that the SByte values use sign-and-magnitude representation for positive values, and two's complement representation for negative values. In order to perform a meaningful bitwise operation, the values must be converted to two equivalent representations, and information about the sign bit must be preserved. The following example does this to mask out bits 2 and 4 of an array of 8-bit signed and unsigned values.

using System;
using System.Collections.Generic;
using System.Globalization;

public struct ByteString
{
   public string Value;
   public int Sign;
}

public class Example
{
   public static void Main()
   {
      ByteString[] values = CreateArray(-15, 123, 245);

      byte mask = 0x14;        // Mask all bits but 2 and 4.

      foreach (ByteString strValue in values) {
         byte byteValue = Byte.Parse(strValue.Value, NumberStyles.AllowHexSpecifier);
         Console.WriteLine("{0} ({1}) And {2} ({3}) = {4} ({5})", 
                           strValue.Sign * byteValue, 
                           Convert.ToString(byteValue, 2), 
                           mask, Convert.ToString(mask, 2), 
                           (strValue.Sign & Math.Sign(mask)) * (byteValue & mask), 
                           Convert.ToString(byteValue & mask, 2));
      }
   }

   private static ByteString[] CreateArray(params int[] values)
   {
      List<ByteString> byteStrings = new List<ByteString>();

      foreach (object value in values) {
         ByteString temp = new ByteString();
         int sign = Math.Sign((int) value);
         temp.Sign = sign;

         // Change two's complement to magnitude-only representation.
         temp.Value = Convert.ToString(((int) value) * sign, 16);

         byteStrings.Add(temp);
      }
      return byteStrings.ToArray();
   }
}
// The example displays the following output:
//       -15 (1111) And 20 (10100) = 4 (100)
//       123 (1111011) And 20 (10100) = 16 (10000)
//       245 (11110101) And 20 (10100) = 20 (10100)