How To Generate MD5 Hash Code Using C#.NET

MD5 Hash code is a unique string of characters that can be generated for a given character string. This Hash code is very important when you compare string values. It is not technically correct to compare two string directly. Good method is generate Hash code for both the strings and compare those Hash codes. Virtually it is agreed that accuracy of Hash code comparison is much higher. Not only to compare two strings, we can use Hash code to compare two files as well. There it is required to read a file as byte stream and generate Hash code for that stream. To compare that stream with second file you need generate Hash code for second file as well  using same method and compare those Hash codes. Using this method you can check whether any changes has happened to the content of the file as well as meta data of the file. So that MD5 Hash code is really important in various scenarios. Most of the programming languages are directly support for MD5 generation. Even SQL commands are available to generate Hash code directly at database level. Here I am explaining one of the methods that can be easily used.

First step is to generate MD5 Hash for any object is convert that object into a byte array. For this we take MemoryStream and BinaryFormatter objects.

MemoryStream fs = new MemoryStream();

BinaryFormatter formatter = new BinaryFormatter();

Serialize() method is used to directly convert object into MemoryStream. Before this operation to be thread-safe we should lock the object.

private static readonly Object locker = new Object();

lock (locker)

{

    formatter.Serialize(fs, objectToSerialize);

}

return fs.ToArray();

Now we are ready to generate a MD5 Hash code for above serialized byte array. MD5CryptoServiceProvider is used to compute Hash for given stream of bytes. Finaly convert the each byte to Hex and appending it to the StringBuilder to build final string.

MD5 md5 = new MD5CryptoServiceProvider();

try

{

    byte[] result = md5.ComputeHash(objectAsBytes);

    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < result.Lenght; i++)

    {

         sb.Append(result[i].ToString("X2"));

    }

    return sb.ToString();

}

catch (ArgumentNullException ex)

{

    // Exception Message

}

You need to include followings

using System.Security.Cryptography;

using System.Runtime.Serialization.Formatters.Binary;

using System.Runtime.Serialization;

using System.Reflection;

using System.Threading;

Now you done! This method can be used for any string or any file to compute MD5 Hash code. If you need any further clarification please list them under comments section. You can find more details here:
Illustrated C# 2008 (Windows.Net), Pro C# 2008 and the .NET 3.5 Platform, Fourth Edition (Windows.Net), C# 3.0 Design Patterns, Head First C#