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HashAlgorithm.TransformFinalBlock Method

Computes the hash value for the specified region of the specified byte array.

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

public byte[] TransformFinalBlock (
	byte[] inputBuffer,
	int inputOffset,
	int inputCount
)
public final byte[] TransformFinalBlock (
	byte[] inputBuffer, 
	int inputOffset, 
	int inputCount
)
public final function TransformFinalBlock (
	inputBuffer : byte[], 
	inputOffset : int, 
	inputCount : int
) : byte[]
Not applicable.

Parameters

inputBuffer

The input to compute the hash code for.

inputOffset

The offset into the byte array from which to begin using data.

inputCount

The number of bytes in the byte array to use as data.

Return Value

An array that is a copy of the part of the input that is hashed.

Exception typeCondition

ArgumentException

inputCount uses an invalid value.

-or-

inputBuffer has an invalid offset length.

ArgumentNullException

inputBuffer is a null reference (Nothing in Visual Basic).

ArgumentOutOfRangeException

inputOffset is out of range. This parameter cannot be a non-negative number.

ObjectDisposedException

The object has already been disposed.

You must call the TransformFinalBlock method after calling the TransformBlock method but before you retrieve the final hash value.

Note that the return value of this method is not the hash value, but only a copy of the hashed part of the input data. To retrieve the final hashed value after calling the TransformFinalBlock method, get the byte array contained in the Hash property.

The following code examples use the TransformFinalBlock method with the TransformBlock method to hash a string.

using System;
using System.Security.Cryptography;
using System.Text;

class MainClass
{
	public static void Main()
	{
		RandomNumberGenerator rnd = RandomNumberGenerator.Create();

		byte[] input = new byte[20];
		rnd.GetBytes(input);

		Console.WriteLine("Input        : {0}\n", BytesToStr(input));
		PrintHash(input);
		PrintHashOneBlock(input);
		PrintHashMultiBlock(input, 1);
		PrintHashMultiBlock(input, 2);
		PrintHashMultiBlock(input, 3);
		PrintHashMultiBlock(input, 5);
		PrintHashMultiBlock(input, 10);
		PrintHashMultiBlock(input, 11);
		PrintHashMultiBlock(input, 19);
		PrintHashMultiBlock(input, 20);
		PrintHashMultiBlock(input, 21);
	}

	public static string BytesToStr(byte[] bytes)
	{
		StringBuilder str = new StringBuilder();

		for (int i = 0; i < bytes.Length; i++)
			str.AppendFormat("{0:X2}", bytes[i]);

		return str.ToString();
	}

	public static void PrintHash(byte[] input)
	{
		SHA256Managed sha = new SHA256Managed();
		Console.WriteLine("ComputeHash  : {0}", BytesToStr(sha.ComputeHash(input)));
	}

	public static void PrintHashOneBlock(byte[] input)
	{
		SHA256Managed sha = new SHA256Managed();
		sha.TransformFinalBlock(input, 0, input.Length);
		Console.WriteLine("FinalBlock   : {0}", BytesToStr(sha.Hash));
	}

	public static void PrintHashMultiBlock(byte[] input, int size)
	{
		SHA256Managed sha = new SHA256Managed();
		int offset = 0;

		while (input.Length - offset >= size)
			offset += sha.TransformBlock(input, offset, size, input, offset);

		sha.TransformFinalBlock(input, offset, input.Length - offset);
		Console.WriteLine("MultiBlock {0:00}: {1}", size, BytesToStr(sha.Hash));
	}

}

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0

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