Hashing gone wrong
Public Shared Function Compute(ByVal text As String, ByVal algorithm As String, Optional ByVal salt() As Byte = Nothing) As String
    If salt Is Nothing Then
        Dim saltSize As Integer = 8
        salt = New Byte(saltSize - 1) {}

        Dim rng As New RNGCryptoServiceProvider
        rng.GetNonZeroBytes(salt)
    End If

    Dim textBytes As Byte() = Encoding.UTF8.GetBytes(text)
    Dim saltedTextBytes() As Byte = New Byte(textBytes.Length + salt.Length - 1) {}
    For i As Integer = 0 To textBytes.Length - 1
        saltedTextBytes(i) = textBytes(i)
    Next i

    For i As Integer = 0 To salt.Length - 1
        saltedTextBytes(textBytes.Length + i) = salt(i)
    Next i

    Dim hash As HashAlgorithm
    If algorithm Is Nothing Then
        algorithm = ""
    End If

    Select Case algorithm.ToUpper
        Case "SHA1" : hash = New SHA1Managed
        Case "SHA256" : hash = New SHA256Managed
        Case "SHA384" : hash = New SHA384Managed
        Case "SHA512" : hash = New SHA512Managed
        Case Else : hash = New MD5CryptoServiceProvider
    End Select

    Dim hashBytes As Byte() = hash.ComputeHash(saltedTextBytes)
    Dim saltedHash() As Byte = New Byte(hashBytes.Length + salt.Length - 1) {}
    For i As Integer = 0 To hashBytes.Length - 1
        saltedHash(i) = hashBytes(i)
    Next i

    For i As Integer = 0 To salt.Length - 1
        saltedHash(hashBytes.Length + i) = salt(i)
    Next i

    Dim hashValue As String = Convert.ToBase64String(saltedHash)

    Return Left(hashValue, 36)
End Function

' The email address needs to be valid
        Dim pattern As String = "^(?("")("".+?""@)|(([0-9a-zA-Z]((.(?!.))|[-!#$%&'*+/=?^`{}|~w])*)(?<=[0-9a-zA-Z])@))(?([)([(d{1,3}.){3}d{1,3}])|(([0-9a-zA-Z][-w]*[0-9a-zA-Z].)+[a-zA-Z]{2,6}))$"
        Dim match As Match = Regex.Match(txtEmail.Text, pattern)
        If match.Success Then
            'Hash the user's password before entering it into the database.
            Dim pass As String = Crypt.Compute(txtPass.Text, "SHA512", Nothing)

            ' Enter the information from the form into the database.
            Dim sql As String = "INSERT INTO Users(Username, Password, EmailAddress) " & _
                "VALUES(@User, @Pass, @Email)"
            Dim cmd As New SqlCommand(sql, conn)
            cmd.Parameters.AddWithValue("@User", txtName.Text)
            cmd.Parameters.AddWithValue("@Pass", pass)
            cmd.Parameters.AddWithValue("@Email", txtEmail.Text)

            conn.Open()
            cmd.ExecuteNonQuery()
            conn.Close()
        Else
            lblError.Text = "Invalid email address. Please correct."
            lblError.ForeColor = Drawing.Color.Red
        End If

Dim pass As String = Crypt.Compute(txtPass.Text, "SHA512", Nothing)

            Dim UserData As New DataSet
            Dim UserAdapter As New SqlDataAdapter
            UserAdapter.SelectCommand = New SqlCommand("SELECT * FROM Users " & _
                                                       "WHERE Username = @User AND Password = @Pass", conn)
            UserAdapter.SelectCommand.Parameters.AddWithValue("@User", txtUser.Text)
            UserAdapter.SelectCommand.Parameters.AddWithValue("@Pass", pass)
            UserAdapter.Fill(UserData)

            If UserData.Tables(0).Rows.Count <> 1 Then
                lblError.Text = "Invalid username or password."
                lblError.ForeColor = Drawing.Color.Red
                Session("LoginAttempt") = CInt(Session("LoginAttempt")) + 1
            Else
                Session("LoggedIn") = True
                Response.Redirect("Home.aspx")
            End If

Dim thePass As String = "MyPassword"
Dim theSalt As String = "salt"

Dim pass As String = Compute(thePass, "SHA512", Encoding.UTF8.GetBytes(theSalt))
Console.WriteLine(pass)
Dim pass2 As String = Compute(thePass, "SHA512", Encoding.UTF8.GetBytes(theSalt))
Console.WriteLine(pass2) 'pass and pass2 are identical