This snippet function hashes a string into an MD5. The function will throw an error if an empty string is provided. Just copy and paste this into a console application, set the Sub Main() as the start up object and run it! You will see how the same hash is created for the "Test" string and a different hash is created for the "Test1" string. If you've got any problems with this snippet just comment or private message me.

Imports System.Security.Cryptography
Imports System.Text.Encoding

Class HashingClass

    'Testing your application
    Shared Sub Main()
        Dim objectInstance As New HashingClass
        Try
            Console.WriteLine(objectInstance.GetStringMD5("Test"))
            Console.WriteLine(objectInstance.GetStringMD5("Test"))
            Console.WriteLine(objectInstance.GetStringMD5("Test1"))
            Console.WriteLine(objectInstance.GetStringMD5(""))
        Catch md5Exception As Exception
            Console.WriteLine(String.Format("Error encountered: {0} - Thrown by: {1}", _
                                            md5Exception.Message, _
                                            md5Exception.TargetSite.Name))
        Finally
            Console.ReadLine()
        End Try
    End Sub

    'The following function hashes a given string using MD5 ...
    Function GetStringMD5(ByVal dataToHash As String) As String
        If dataToHash = String.Empty Then
            Throw New ApplicationException("Cannot hash empty string!")
        Else
            Dim hashMechanism As HashAlgorithm = HashAlgorithm.Create("MD5")
            Dim data = [Default].GetBytes(dataToHash)
            Dim finalHash = hashMechanism.ComputeHash(data)
            Return [Default].GetString(finalHash)
        End If
    End Function

End Class