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BitConverter.ToUInt64 Method

Returns a 64-bit unsigned integer converted from eight bytes at a specified position in a byte array.

This API is not CLS-compliant. 

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

[CLSCompliantAttribute(false)]
public static ulong ToUInt64(
	byte[] value,
	int startIndex
)

Parameters

value
Type: System.Byte[]

An array of bytes.

startIndex
Type: System.Int32

The starting position within value.

Return Value

Type: System.UInt64
A 64-bit unsigned integer formed by the eight bytes beginning at startIndex.

ExceptionCondition
ArgumentException

startIndex is greater than or equal to the length of value minus 7, and is less than or equal to the length of value minus 1.

ArgumentNullException

value is null.

ArgumentOutOfRangeException

startIndex is less than zero or greater than the length of value minus 1.

The ToUInt64 method converts the bytes from index startIndex to startIndex + 7 to a UInt64 value. The order of bytes in the array must reflect the endianness of the computer system's architecture; for more information, see the Remarks section of the BitConverter class topic.

The following code example converts elements of Byte arrays to UInt64 values with the ToUInt64 method.

// Example of the BitConverter.ToUInt64 method. 
using System;

class BytesToUInt64Demo
{
    const string formatter = "{0,5}{1,27}{2,24}";

    // Convert eight byte array elements to a ulong and display it. 
    public static void BAToUInt64( byte[ ] bytes, int index )
    {
        ulong value = BitConverter.ToUInt64( bytes, index );

        Console.WriteLine( formatter, index, 
            BitConverter.ToString( bytes, index, 8 ), value );
    }

    // Display a byte array, using multiple lines if necessary. 
    public static void WriteMultiLineByteArray( byte[ ] bytes )
    {
        const int rowSize = 20;
        int iter;

        Console.WriteLine( "initial byte array" );
        Console.WriteLine( "------------------" );

        for( iter = 0; iter < bytes.Length - rowSize; iter += rowSize )
        {
            Console.Write( 
                BitConverter.ToString( bytes, iter, rowSize ) );
            Console.WriteLine( "-" );
        }

        Console.WriteLine( BitConverter.ToString( bytes, iter ) );
        Console.WriteLine( );
    }

    public static void Main( )
    {
        byte[ ] byteArray = {
            255, 255, 255,   0,   0,   0,   0,   0,   0,   0, 
              0,   1,   0,   0,   0, 100, 167, 179, 182, 224, 
             13,   0, 202, 154,  59,   0,   0,   0,   0, 170, 
            170, 170, 170, 170, 170,   0,   0, 232, 137,   4, 
             35, 199, 138, 255, 255, 255, 255, 255, 255, 255, 
            255, 127 };

        Console.WriteLine( 
            "This example of the BitConverter.ToUInt64( byte[ ], " +
            "int ) \nmethod generates the following output. It " +
            "converts elements \nof a byte array to ulong values.\n" );

        WriteMultiLineByteArray( byteArray );

        Console.WriteLine( formatter, "index", "array elements", 
            "ulong" );
        Console.WriteLine( formatter, "-----", "--------------", 
            "------" );

        // Convert byte array elements to ulong values.
        BAToUInt64( byteArray, 3 );
        BAToUInt64( byteArray, 0 );
        BAToUInt64( byteArray, 21 );
        BAToUInt64( byteArray, 7 );
        BAToUInt64( byteArray, 29 );
        BAToUInt64( byteArray, 13 );
        BAToUInt64( byteArray, 35 );
        BAToUInt64( byteArray, 44 );
        BAToUInt64( byteArray, 43 );
    }
}

/*
This example of the BitConverter.ToUInt64( byte[ ], int )
method generates the following output. It converts elements
of a byte array to ulong values.

initial byte array
------------------
FF-FF-FF-00-00-00-00-00-00-00-00-01-00-00-00-64-A7-B3-B6-E0-
0D-00-CA-9A-3B-00-00-00-00-AA-AA-AA-AA-AA-AA-00-00-E8-89-04-
23-C7-8A-FF-FF-FF-FF-FF-FF-FF-FF-7F

index             array elements                   ulong
-----             --------------                  ------
    3    00-00-00-00-00-00-00-00                       0
    0    FF-FF-FF-00-00-00-00-00                16777215
   21    00-CA-9A-3B-00-00-00-00              1000000000
    7    00-00-00-00-01-00-00-00              4294967296
   29    AA-AA-AA-AA-AA-AA-00-00         187649984473770
   13    00-00-64-A7-B3-B6-E0-0D     1000000000000000000
   35    00-00-E8-89-04-23-C7-8A    10000000000000000000
   44    FF-FF-FF-FF-FF-FF-FF-7F     9223372036854775807
   43    FF-FF-FF-FF-FF-FF-FF-FF    18446744073709551615
*/

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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