HashAlgorithm.TransformBlock Method (Byte[], Int32, Int32, Byte[], Int32)


Computes the hash value for the specified region of the input byte array and copies the specified region of the input byte array to the specified region of the output byte array.

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

public int TransformBlock(
	byte[] inputBuffer,
	int inputOffset,
	int inputCount,
	byte[] outputBuffer,
	int outputOffset


Type: System.Byte[]

The input to compute the hash code for.

Type: System.Int32

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

Type: System.Int32

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

Type: System.Byte[]

A copy of the part of the input array used to compute the hash code.

Type: System.Int32

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

Return Value

Type: System.Int32

The number of bytes written.

Exception Condition

inputCount uses an invalid value.


inputBuffer has an invalid length.


inputBuffer is null.


inputOffset is out of range. This parameter requires a non-negative number.


The object has already been disposed.

You must call the TransformBlock method before calling the TransformFinalBlock method. You must call both methods before you retrieve the final hash value.

To retrieve the final hash value after calling the TransformFinalBlock method, get the byte array contained within the Hash property.

Calling the TransformBlock method with different input and output arrays results in an IOException.

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];

		Console.WriteLine("Input        : {0}\n", BytesToStr(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));


.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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