BigInteger.ToByteArray Method

Definition

Namespace:

System.Numerics

Assembly:

System.Runtime.Numerics.dll

Overloads

ToByteArray()	Converts a BigInteger value to a byte array.
ToByteArray(Boolean, Boolean)	Returns the value of this BigInteger as a byte array using the fewest number of bytes possible. If the value is zero, returns an array of one byte whose element is 0x00.

ToByteArray()

Source:

BigInteger.cs

Converts a BigInteger value to a byte array.

public:
 cli::array <System::Byte> ^ ToByteArray();

public byte[] ToByteArray ();

member this.ToByteArray : unit -> byte[]

Public Function ToByteArray () As Byte()

Returns

Byte[]

The value of the current BigInteger object converted to an array of bytes.

Examples

The following example illustrates how some BigInteger values are represented in byte arrays.

using System;
using System.Numerics;

public class Example
{
   static byte[] bytes;

   public static void Main()
   {
      BigInteger[] numbers = { BigInteger.MinusOne, BigInteger.One,
                               BigInteger.Zero, 120, 128, 255, 1024,
                               Int64.MinValue, Int64.MaxValue,
                               BigInteger.Parse("90123123981293054321") };
      foreach (BigInteger number in numbers)
      {
         bytes = number.ToByteArray();
         Console.Write("{0} ({1}) -> ", number, number.ToString(GetSpecifier()));
         Console.Write("{0} bytes: ", bytes.Length);
         foreach (byte byteValue in bytes)
            Console.Write("{0:X2} ", byteValue);

         Console.WriteLine();
      }
   }

   private static string GetSpecifier()
   {
      return "X" + (bytes.Length * 2).ToString();
   }
}
// The example displays the following output:
//    -1 (FF) -> 1 bytes: FF
//    1 (01) -> 1 bytes: 01
//    0 (00) -> 1 bytes: 00
//    120 (78) -> 1 bytes: 78
//    128 (0080) -> 2 bytes: 80 00
//    255 (00FF) -> 2 bytes: FF 00
//    1024 (0400) -> 2 bytes: 00 04
//    -9223372036854775808 (8000000000000000) -> 8 bytes: 00 00 00 00 00 00 00 80
//    9223372036854775807 (7FFFFFFFFFFFFFFF) -> 8 bytes: FF FF FF FF FF FF FF 7F
//    90123123981293054321 (04E2B5A7C4A975E971) -> 9 bytes: 71 E9 75 A9 C4 A7 B5 E2 04

open System
open System.Numerics

let numbers =
    [| BigInteger.MinusOne
       BigInteger.One
       BigInteger.Zero
       120
       128
       255
       1024
       Int64.MinValue
       Int64.MaxValue
       BigInteger.Parse("90123123981293054321") |]

for number in numbers do
    let bytes = number.ToByteArray()
    printf $"""{number} ({number.ToString("X" + (bytes.Length * 2).ToString())}) -> """
    printf $"{bytes.Length} bytes: "

    for byteValue in bytes do
        printf $"{byteValue:X2} "

    printfn ""

// The example displays the following output:
//    -1 (FF) -> 1 bytes: FF
//    1 (01) -> 1 bytes: 01
//    0 (00) -> 1 bytes: 00
//    120 (78) -> 1 bytes: 78
//    128 (0080) -> 2 bytes: 80 00
//    255 (00FF) -> 2 bytes: FF 00
//    1024 (0400) -> 2 bytes: 00 04
//    -9223372036854775808 (8000000000000000) -> 8 bytes: 00 00 00 00 00 00 00 80
//    9223372036854775807 (7FFFFFFFFFFFFFFF) -> 8 bytes: FF FF FF FF FF FF FF 7F
//    90123123981293054321 (04E2B5A7C4A975E971) -> 9 bytes: 71 E9 75 A9 C4 A7 B5 E2 04

Imports System.Numerics

Module Example
   Dim bytes() As Byte
      
   Public Sub Main()
      Dim numbers() As BigInteger = { BigInteger.MinusOne, BigInteger.One, 
                                      BigInteger.Zero, 120, 128, 255, 1024, 
                                      Int64.MinValue, Int64.MaxValue, 
                                      BigInteger.Parse("90123123981293054321") }
      For Each number As BigInteger In numbers
         bytes = number.ToByteArray()
         Console.Write("{0} ({1}) -> ", number, number.ToString(GetSpecifier()))
         Console.Write("{0} bytes: ", bytes.Length)
         For Each byteValue As Byte In bytes
            Console.Write("{0:X2} ", byteValue)
         Next
         Console.WriteLine()
      Next   
   End Sub
   
   Private Function GetSpecifier() As String
      Return "X" + CStr(bytes.Length * 2)
   End Function
End Module
' The example displays the following output:
'    -1 (FF) -> 1 bytes: FF
'    1 (01) -> 1 bytes: 01
'    0 (00) -> 1 bytes: 00
'    120 (78) -> 1 bytes: 78
'    128 (0080) -> 2 bytes: 80 00
'    255 (00FF) -> 2 bytes: FF 00
'    1024 (0400) -> 2 bytes: 00 04
'    -9223372036854775808 (8000000000000000) -> 8 bytes: 00 00 00 00 00 00 00 80
'    9223372036854775807 (7FFFFFFFFFFFFFFF) -> 8 bytes: FF FF FF FF FF FF FF 7F
'    90123123981293054321 (04E2B5A7C4A975E971) -> 9 bytes: 71 E9 75 A9 C4 A7 B5 E2 04

Remarks

The individual bytes in the array returned by this method appear in little-endian order. That is, the lower-order bytes of the value precede the higher-order bytes. The first byte of the array reflects the first eight bits of the BigInteger value, the second byte reflects the next eight bits, and so on. For example, the value 1024, or 0x0400, is stored as the following array of two bytes:

Element	Byte value
0	0x00
1	0x04

Negative values are written to the array using two's complement representation in the most compact form possible. For example, -1 is represented as a single byte whose value is 0xFF instead of as an array with multiple elements, such as 0xFF, 0xFF or 0xFF, 0xFF, 0xFF, 0xFF.

Because two's complement representation always interprets the highest-order bit of the last byte in the array (the byte at position Array.Length- 1) as the sign bit, the method returns a byte array with an extra element whose value is zero to disambiguate positive values that could otherwise be interpreted as having their sign bits set. For example, the value 120 or 0x78 is represented as a single-byte array: 0x78. However, 128, or 0x80, is represented as a two-byte array: 0x80, 0x00.

You can round-trip a BigInteger value by storing it to a byte array and then restoring it using the BigInteger(Byte[]) constructor.

Caution

If your code modifies the value of individual bytes in the array returned by this method before it restores the value, you must make sure that you do not unintentionally change the sign bit. For example, if your modifications increase a positive value so that the highest-order bit in the last element of the byte array becomes set, you can add a new byte whose value is zero to the end of the array.

ToByteArray(Boolean, Boolean)

Source:

BigInteger.cs

Returns the value of this BigInteger as a byte array using the fewest number of bytes possible. If the value is zero, returns an array of one byte whose element is 0x00.

public byte[] ToByteArray (bool isUnsigned = false, bool isBigEndian = false);

member this.ToByteArray : bool * bool -> byte[]

Public Function ToByteArray (Optional isUnsigned As Boolean = false, Optional isBigEndian As Boolean = false) As Byte()

Parameters

isUnsigned

Boolean

true to use unsigned encoding; otherwise, false.

isBigEndian

Boolean

true to write the bytes in a big-endian byte order; otherwise, false.

Returns

Byte[]

The value of the current BigInteger object converted to an array of bytes.

Exceptions

OverflowException

If isUnsigned is true and Sign is negative.

Remarks

The integer value 33022 can be exported in four different arrays:

Properties	Result
isUnsigned: false, isBigEndian: false	new byte[] { 0xFE, 0x80, 0x00 }
isUnsigned: false, isBigEndian: true	new byte[] { 0x00, 0x80, 0xFE }
isUnsigned: true, isBigEndian: false	new byte[] { 0xFE, 0x80 }
isUnsigned: true, isBigEndian: true	new byte[] { 0x80, 0xFE }