MD5 Class
.NET Framework Class Library
MD5 Class

Represents the abstract class from which all implementations of the MD5 hash algorithm inherit.

Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)
Visual Basic
<ComVisibleAttribute(True)> _
Public MustInherit Class MD5 _
    Inherits HashAlgorithm
C#
[ComVisibleAttribute(true)]
public abstract class MD5 : HashAlgorithm
Visual C++
[ComVisibleAttribute(true)]
public ref class MD5 abstract : public HashAlgorithm
F#
[<AbstractClassAttribute>]
[<ComVisibleAttribute(true)>]
type MD5 =  
    class
        inherit HashAlgorithm
    end

Hash functions map binary strings of an arbitrary length to small binary strings of a fixed length. A cryptographic hash function has the property that it is computationally infeasible to find two distinct inputs that hash to the same value; that is, hashes of two sets of data should match if the corresponding data also matches. Small changes to the data result in large, unpredictable changes in the hash.

The hash size for the MD5 algorithm is 128 bits.

The ComputeHash methods of the MD5 class return the hash as an array of 16 bytes. Note that some MD5 implementations produce a 32-character, hexadecimal-formatted hash. To interoperate with such implementations, format the return value of the ComputeHash methods as a hexadecimal value.

The following code example computes the MD5 hash value of a string and returns the hash as a 32-character, hexadecimal-formatted string. The hash string created by this code example is compatible with any MD5 hash function (on any platform) that creates a 32-character, hexadecimal-formatted hash string.

Visual Basic
Imports System
Imports System.Security.Cryptography
Imports System.Text

Module Example

    ' Hash an input string and return the hash as
    ' a 32 character hexadecimal string.
    Function getMd5Hash(ByVal input As String) As String
        ' Create a new instance of the MD5 object.
        Dim md5Hasher As MD5 = MD5.Create()

        ' Convert the input string to a byte array and compute the hash.
        Dim data As Byte() = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input))

        ' Create a new Stringbuilder to collect the bytes
        ' and create a string.
        Dim sBuilder As New StringBuilder()

        ' Loop through each byte of the hashed data 
        ' and format each one as a hexadecimal string.
        Dim i As Integer
        For i = 0 To data.Length - 1
            sBuilder.Append(data(i).ToString("x2"))
        Next i

        ' Return the hexadecimal string.
        Return sBuilder.ToString()

    End Function


    ' Verify a hash against a string.
    Function verifyMd5Hash(ByVal input As String, ByVal hash As String) As Boolean
        ' Hash the input.
        Dim hashOfInput As String = getMd5Hash(input)

        ' Create a StringComparer an compare the hashes.
        Dim comparer As StringComparer = StringComparer.OrdinalIgnoreCase

        If 0 = comparer.Compare(hashOfInput, hash) Then
            Return True
        Else
            Return False
        End If

    End Function



    Sub Main()
        Dim source As String = "Hello World!"

        Dim hash As String = getMd5Hash(source)

        Console.WriteLine("The MD5 hash of " + source + " is: " + hash + ".")

        Console.WriteLine("Verifying the hash...")

        If verifyMd5Hash(source, hash) Then
            Console.WriteLine("The hashes are the same.")
        Else
            Console.WriteLine("The hashes are not same.")
        End If

    End Sub
End Module
' This code example produces the following output:
'
' The MD5 hash of Hello World! is: ed076287532e86365e841e92bfc50d8c.
' Verifying the hash...
' The hashes are the same.
C#
using System;
using System.Security.Cryptography;
using System.Text;

class Example
{
    // Hash an input string and return the hash as
    // a 32 character hexadecimal string.
    static string getMd5Hash(string input)
    {
        // Create a new instance of the MD5CryptoServiceProvider object.
        MD5 md5Hasher = MD5.Create();

        // Convert the input string to a byte array and compute the hash.
        byte[] data = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input));

        // Create a new Stringbuilder to collect the bytes
        // and create a string.
        StringBuilder sBuilder = new StringBuilder();

        // Loop through each byte of the hashed data 
        // and format each one as a hexadecimal string.
        for (int i = 0; i < data.Length; i++)
        {
            sBuilder.Append(data[i].ToString("x2"));
        }

        // Return the hexadecimal string.
        return sBuilder.ToString();
    }

    // Verify a hash against a string.
    static bool verifyMd5Hash(string input, string hash)
    {
        // Hash the input.
        string hashOfInput = getMd5Hash(input);

        // Create a StringComparer an compare the hashes.
        StringComparer comparer = StringComparer.OrdinalIgnoreCase;

        if (0 == comparer.Compare(hashOfInput, hash))
        {
            return true;
        }
        else
        {
            return false;
        }
    }


    static void Main()
    {
        string source = "Hello World!";

        string hash = getMd5Hash(source);

        Console.WriteLine("The MD5 hash of " + source + " is: " + hash + ".");

        Console.WriteLine("Verifying the hash...");

        if (verifyMd5Hash(source, hash))
        {
            Console.WriteLine("The hashes are the same.");
        }
        else
        {
            Console.WriteLine("The hashes are not same.");
        }

    }
}
// This code example produces the following output:
//
// The MD5 hash of Hello World! is: ed076287532e86365e841e92bfc50d8c.
// Verifying the hash...
// The hashes are the same.
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role not supported), Windows Server 2003 SP2

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

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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A one-liner      Daniel Santa Cruz   |   Edit   |   Show History
Ok, maybe not quite ONE line. This will do the trick: $0$0 $0 $0(requires LINQ)$0 $0$0 $0 $0System.Security.Cryptography.MD5.Create()$0 $0.ComputeHash(Encoding.Default.GetBytes(tohash))$0 $0.Select(x => x.ToString("x2"))$0 $0.Aggregate(new System.Text.StringBuilder(), (acc, x) => acc.Append(x))$0 $0.ToString();$0 $0 $0
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