Insert data into database by linking class to btnRegister - vb.net

Question

I am new for programming and trying to learn VB.net through youtube tutorials.
I created a windows form app for users to create new account.
I am also trying to apply the hash and salt technique to store the password for security reason.
The main issue I have is maintaining successful connection between a two class I called "DatabaseManager" and "DataHandling", codes in "btnRegister" and the database called "Test".
The program runs fine. When I click btnRegister after filling the "txtUsername.Text" and "txtPassword.Text", it gives me error that says "ColumnUser_IDdoes not allow nulls.".
So this is where I keep getting issues. I tried to make it work a lot and I have no idea why it is not recording the new data. Here are my codes. I use V Studio 2012. Please help.
Just to be clear I copied some of the codes from internet and tried to make them work with the class
Imports System
Imports System.IO
Imports System.Text
Imports System.Data.OleDb
Imports System.Data
Imports System.Windows.Forms
Imports System.Data.SqlClient
Imports System.Security.Cryptography
Public Class DatabaseManager
Private Const CONNECTION_STRING As String = "Data Source=(localdb)\Projects;Initial Catalog=Test;Integrated Security=True"
Private connection As SqlConnection = Nothing
Private usersdataadapter As SqlDataAdapter = Nothing
Sub New()
connection = New SqlConnection(CONNECTION_STRING)
usersdataadapter = New SqlDataAdapter("select * from Test", connection)
End Sub
Public Sub Register(ByVal Username As String, ByVal Password As String)
connection.Open()
Dim usersDataset As New DataSet()
usersdataadapter.FillSchema(usersDataset, SchemaType.Source, "Test")
Dim table As DataTable = usersDataset.Tables("Test")
Dim newRecord As DataRow = table.NewRow()
newRecord("Username") = Username
newRecord("Password") = Password
table.Rows.Add(newRecord)
Dim command As New SqlCommandBuilder(usersdataadapter)
usersdataadapter.Update(usersDataset, "Test")
usersDataset.Dispose()
connection.Close()
End Sub
Public Function UsernameAvailable(ByVal username As String) As Boolean
Dim usersDataset As New DataSet()
usersdataadapter.FillSchema(usersDataset, SchemaType.Source, "Test")
usersdataadapter.Fill(usersDataset, "Test")
Dim table As DataTable = usersDataset.Tables("Test")
For i As Integer = 0 To table.Rows.Count - 1
Dim currnetUser As String = table.Rows(i)("Username").ToString().Trim()
If (currnetUser = username) Then
usersDataset.Dispose()
connection.Close()
Return False
End If
Next
Return True
usersDataset.Dispose()
connection.Close()
End Function
Public Function Login(ByVal username As String, ByVal password As String) As Boolean
Dim usersDataset As New DataSet()
usersdataadapter.FillSchema(usersDataset, SchemaType.Source, "Test")
usersdataadapter.Fill(usersDataset, "Test")
Dim table As DataTable = usersDataset.Tables("Test")
For i As Integer = 0 To table.Rows.Count - 1
Dim currnetUser As String = table.Rows(i)("Username").ToString().Trim()
Dim currnetPassword As String = table.Rows(i)("Password").ToString().Trim()
If (currnetUser = username AndAlso currnetPassword = password) Then
usersDataset.Dispose()
connection.Close()
Return True
End If
Next
usersDataset.Dispose()
connection.Close()
Return False
End Function
End Class
Imports System
Imports System.Text
Imports System.Data.OleDb
Imports System.Data
Imports System.Data.SqlClient
Imports System.Windows.Forms
Imports System.Security.Cryptography
Public Class DataHandling
Inherits Form1
Public Shared Function GenerateRandomString() As String
Dim i_key As Integer
Dim Random1 As Single
Dim arrIndex As Int16
Dim sb As New StringBuilder
Dim RandomLetter As String
Dim KeyLetters As String = "abcdefghijklmnopqrstuvwxyz"
Dim KeyNumbers As String = "0123456789"
Dim KeyLength As Integer = 12
Dim LettersArray = KeyLetters.ToCharArray
Dim NumbersArray = KeyNumbers.ToCharArray
For i_key = 1 To KeyLength
Randomize()
Random1 = Rnd()
arrIndex = -1
If (CType(Random1 * 111, Integer)) Mod 2 = 0 Then
Do While arrIndex < 0
arrIndex = _
Convert.ToInt16(LettersArray.GetUpperBound(0) _
* Random1)
Loop
RandomLetter = LettersArray(arrIndex)
If (CType(arrIndex * Random1 * 99, Integer)) Mod 2 <> 0 Then
RandomLetter = LettersArray(arrIndex).ToString
RandomLetter = RandomLetter.ToUpper
End If
sb.Append(RandomLetter)
Else
Do While arrIndex < 0
arrIndex = _
Convert.ToInt16(NumbersArray.GetUpperBound(0) _
* Random1)
Loop
sb.Append(NumbersArray(arrIndex))
End If
Next
Return sb.ToString
End Function
Public Shared Function CheckPassword(ByVal plainText As String, ByVal passwordHash As Byte(), ByVal salt As Byte()) As Boolean
Dim encoding As New System.Text.UTF8Encoding
'Retrieve Salt String from byte array
Dim saltStr As String = encoding.GetString(salt)
Dim hashable As String = Trim(plainText) & Trim(saltStr)
' Convert into hash strings
Dim testhash As String = EncryptStringAsHash(hashable)
Dim realHash As String = encoding.GetString(passwordHash)
' Compare and return result
Return testhash = realHash
End Function
Public Shared Function EncryptStringAsHash(ByVal value As String) As String
Dim encoding As New System.Text.UTF8Encoding
Dim stringBytes As Byte() = encoding.GetBytes(value)
Dim SHhash As SHA512Managed = New SHA512Managed
Dim hash As String = Convert.ToBase64String(SHhash.ComputeHash(stringBytes))
Return hash
End Function
Public Shared Function ConvertStringToByteArray(ByVal value As String) As Byte()
Dim encoding As New System.Text.UTF8Encoding
Return encoding.GetBytes(value)
End Function
End Class
Imports System.IO
Imports System.Text
Imports System.Security.Cryptography
Imports System.Data.OleDb
Imports System.Windows.Forms
Imports System.Data.OleDb.OleDbConnection
Imports System.Data.SqlClient
Public Class Form1
Dim maxrows As Integer
Dim incdec As Integer
Dim con As New OleDb.OleDbConnection
Dim dbprovider As String
Dim dbsource As String
Dim ds As New DataSet
Dim da As OleDb.OleDbDataAdapter
Dim sql As String
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim con As New OleDbConnection
Dim dbprovider As String
Dim dbsource As String
dbprovider = "PROVIDER = Microsoft.ACE.OLEDB.12.0;"
dbsource = "Data Source=(localdb)\Projects;Initial Catalog=Test;Integrated Security=True"
con.ConnectionString = dbprovider & dbsource
End Sub
Private Sub btnRegister_Click(sender As Object, e As EventArgs) Handles btnRegister.Click
Dim dbmanager As New DatabaseManager
Dim Data As New DataHandling
'Generate Hash and Salt for password
Dim salt As String = DataHandling.GenerateRandomString
Dim hashable As String = Trim(txtPassword.Text) & Trim(salt) 'txtPassword.Text used to be password
Dim hash As String = DataHandling.EncryptStringAsHash(hashable)
Dim confirmationId As String = System.Guid.NewGuid.ToString
Dim reg As user
reg.Username = txtUsername.Text 'txtUsername.Text used to be username
reg.Password = DataHandling.ConvertStringToByteArray(hash)
reg.Salt = DataHandling.ConvertStringToByteArray(salt)
If dbmanager.UsernameAvailable(txtUsername.Text) Then
dbmanager.Register(txtUsername.Text, txtPassword.Text)
Dim password As String
If txtPassword.Text = String.Empty Then
password = "217tABCDEF42#$tolq"
Else
password = txtPassword.Text
End If
Dim salt As String = GenerateRandomString(12)
Dim hashable As String = Trim(password) & Trim(salt)
MsgBox("Hashable = " & hashable)
Dim hash As String = EncryptStringAsHash(hashable)
CheckPassword(password, ConvertStringToByteArray(hash), ConvertStringToByteArray(salt))
frmAccessGranted.Show()
Me.Hide()
Else
MessageBox.Show("Cannot Register, Username Already Taken!")
End If
End Sub
Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
txtUsername.Clear()
txtPassword.Clear()
End Sub
End Class

Answer 1

I think your User table User_id value is just missing Identity Specification option. It makes the User_id field to be generated automatically and increased by 1 (by default) for each User you add into
If you have SQL Server management studio you can put this option on:
Right click User table -> Select "Desing" -> Select "User_id" field -> in "Column Propetries" window put "Indentity Specification" option to "Yes" and save
Example SQL Command to create table could be something like this:
CREATE TABLE User (User_id BIGINT IDENTITY NOT NULL, Username NVARCHAR(100) NOT NULL, Password NVARCHAR(100) NOT NULL)

Answer 2

The problem in your code is not in the VB side, it is in the database.
You have set primary key to UserId but you are not passing any values to the userId, you are just passing values to the user name and password.
So there are two ways to solve this issues
you can send userid also from the VB code
you can just make the column UserId as autoincrement field by the following code
CREATE TABLE [dbo].[Test1](
[id] [int] IDENTITY(1,1) NOT NULL,
YourColumnname1 datatype,
YourColumnname2 datatype
)
This works only in the later versions of sqlserver 2008
alter table tablename
alter column columnname
add Identity(100,1)
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