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Byte Structure

Represents an 8-bit unsigned integer.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Structure Byte _
	Implements IComparable, IFormattable, IConvertible, IComparable(Of Byte),  _
	IEquatable(Of Byte)
'Usage
Dim instance As Byte

Byte is an immutable value type that represents unsigned integers with values that range from 0 (which is represented by the Byte.MinValue constant) to 255 (which is represented by the Byte.MaxValue constant). The .NET Framework also includes a signed 8-bit integer value type, SByte, which represents values that range from -128 to 127.

Instantiating a Byte Value

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.

    Dim value1 As Byte = 64
    Dim value2 As Byte = 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, its fractional part is truncated. The following example assigns several numeric values to Byte variables.

    Dim int1 As Integer = 128
    Try 
       Dim value1 As Byte = CByte(int1)
       Console.WriteLine(value1)
    Catch e As OverflowException
       Console.WriteLine("{0} is out of range of a byte.", int1)
    End Try 
    
    Dim dbl2 As Double = 3.997
    Try 
       Dim value2 As Byte = CByte(dbl2)
       Console.WriteLine(value2)
    Catch e As OverflowException
       Console.WriteLine("{0} is out of range of a byte.", dbl2)
    End Try    
    ' 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.

    Dim numbers() As Integer = { Int32.MinValue, -1, 0, 121, 340, Int32.MaxValue }
    Dim result As Byte
    For Each number As Integer 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 e As OverflowException
          Console.WriteLine("The {0} value {1} is outside the range of the Byte type.", _
                            number.GetType().Name, number)
       End Try 
    Next 
    ' 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.

    Dim string1 As String = "244" 
    Try 
       Dim byte1 As Byte = Byte.Parse(string1)
       Console.WriteLine(byte1)
    Catch e As OverflowException
       Console.WriteLine("'{0}' is out of range of a byte.", string1)
    Catch e As FormatException
       Console.WriteLine("'{0}' is out of range of a byte.", string1)
    End Try 
    
    Dim string2 As String = "F9" 
    Try 
       Dim byte2 As Byte = Byte.Parse(string2, _
                                 System.Globalization.NumberStyles.HexNumber)
       Console.WriteLine(byte2)
    Catch e As OverflowException
       Console.WriteLine("'{0}' is out of range of a byte.", string2)
    Catch e As FormatException
       Console.WriteLine("'{0}' is out of range of a byte.", string2)
    End Try 
    ' The example displays the following output: 
    '       244 
    '       249
    

Performing Operations on Byte Values

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.

Representing a Byte as a String

The Byte type provides full support for standard and custom numeric format strings. (For more information, see Formatting Overview, 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.

Dim numbers() As Byte = { 0, 16, 104, 213 }
For Each number As Byte 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"))
Next    
' 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.

Dim numbers() As Byte = { 0, 16, 104, 213 }
Console.WriteLine("{0}   {1,8}   {2,5}   {3,5}", _
                  "Value", "Binary", "Octal", "Hex")
For Each number As Byte 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))
Next       
' 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      

Working with Non-Decimal Byte Values

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.

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.

Imports System.Globalization

Module Example
   Public Sub Main()
      Dim values() As String = { Convert.ToString(12, 16), _
                                 Convert.ToString(123, 16), _
                                 Convert.ToString(245, 16) }

      Dim mask As Byte = &hFE
      For Each value As String In values
         Dim byteValue As Byte = Byte.Parse(value, NumberStyles.AllowHexSpecifier)
         Console.WriteLine("{0} And {1} = {2}", byteValue, mask, _ 
                           byteValue And mask)
      Next          
   End Sub 
End Module 
' 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.

Imports System.Collections.Generic
Imports System.Globalization

Public Structure ByteString
   Public Value As String 
   Public Sign As Integer 
End Structure 

Module Example
   Public Sub Main()
      Dim values() As ByteString = CreateArray(-15, 123, 245)

      Dim mask As Byte = &h14        ' Mask all bits but 2 and 4.

      For Each strValue As ByteString In values
         Dim byteValue As Byte = 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 And Math.Sign(mask)) * (byteValue And mask), _
                           Convert.ToString(byteValue And mask, 2))
      Next          
   End Sub 

   Private Function CreateArray(ParamArray values() As Object) As ByteString()
      Dim byteStrings As New List(Of ByteString)
      For Each value As Object In values
         Dim temp As New ByteString()
         Dim sign As Integer = Math.Sign(value)
         temp.Sign = sign
         ' Change two's complement to magnitude-only representation.
         value = value * sign

         temp.Value = Convert.ToString(value, 16)
         byteStrings.Add(temp)
      Next 
      Return byteStrings.ToArray()
   End Function    
End Module 
' 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)

All members of this type are thread safe. Members that appear to modify instance state actually return a new instance initialized with the new value. As with any other type, reading and writing to a shared variable that contains an instance of this type must be protected by a lock to guarantee thread safety.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0
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