vb.net how to create the login permission - vb.net

Question

Private Sub Edit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Edit.Click
LoginForm.ShowDialog()
If Me.DataGridView1.Rows.Count > 0 Then
If Me.DataGridView1.SelectedRows.Count > 0 Then
Dim intcid1 As Integer = Me.DataGridView1.SelectedRows(0).Cells("ID").Value
'open connection
If Not cn3.State = ConnectionState.Open Then
cn3.Open()
End If
'get data into datatable
Dim da As New OleDb.OleDbDataAdapter("SELECT * FROM stock " & _
" WHERE cid=" & intcid1, cn3)
Dim dt As New DataTable
da.Fill(dt)
Me.txtbarcode.Text = intcid1
Me.txtdetail1.Text = dt.Rows(0).Item("CheckerDetail")
Me.txtbarcode.Tag = intcid1
'change button save to update
Me.save.Text = "Update"
'disable button edit
'Me.Edit.Enabled = True
Me.save.Enabled = True
End If
End If
cn3.Close()
End Sub
Private Sub save_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles save.Click
Dim cmd As New OleDb.OleDbCommand
If Not cn3.State = ConnectionState.Open Then
'open connection if it is not open yet
cn3.Open()
End If
cmd.Connection = cn3
cmd.CommandText = "INSERT INTO stock([checkercid],[CheckerName],[ShipQuantity],[Date],[CompanyName],[CheckerDetail]) " &
"VALUES( '" & getLastNumber().ToString & "','" & Me.txtCN.Text & "', '" & Me.txtQty.Text & "', '" & Date.Now.ToString("yyyy-MM-dd HH:mm:ss") & "', '" & Me.txtCompanyN.Text & "', '" & Me.txtdetail1.Text & "')"
'Error message if user not fill yhe textbox
If txtdetail1.Text.Trim = "" Then
MessageBox.Show("Please Insert Data", "Error Message")
Exit Sub
End If
cmd.CommandText = "UPDATE stock " & _
" SET" & _
" [CheckerDetail]='" & Me.txtdetail1.Text & "'" & _
" WHERE [cid]=" & DataGridView1("ID", DataGridView1.CurrentCell.RowIndex).Value
MsgBox("Update Data Successful", MsgBoxStyle.OkOnly, "Message")
cmd.ExecuteNonQuery()
Me.btnClear.PerformClick()
RefreshData1()
cn3.Close()
End Sub

Answer 1

I moved things around trying to keep the User Interface code in the Form and the Data Access code in your class. You had Retries in 2 different places. You only need it in one. boolresetPassword is never used in your code. Since you are hard coding the password don't set a bunch of properties of the class in the form. Just put your connection string in the constructor of the connection in the class. The validated data for the LogIn function is passed to the function.
You don't need all those properties in your class. Just add your connection string. You can pass your Select statement and the connection directly to the constructor of the command. Don't use .AddWithValue. See http://www.dbdelta.com/addwithvalue-is-evil/
and
https://blogs.msmvps.com/jcoehoorn/blog/2014/05/12/can-we-stop-using-addwithvalue-already/
and another one:
https://dba.stackexchange.com/questions/195937/addwithvalue-performance-and-plan-cache-implications
I changed the Select to retrieve Count which is all you need to know.
As far as the Cancel button ask a new question with the code for the cancel button.
Public Class LoginForm
Private Retrys As Integer 'Integers automatically initialize to zero
Private Sub Ok_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Ok.Click
If Retrys = 2 Then
MessageBox.Show("Sorry, you have exceeded the maximum number of attempts to login")
Close()
End If
Dim AppLogin As New ApplicatioLogin
'Do your validation here; not in the Data Access code.
If Not String.IsNullOrWhiteSpace(un.Text) AndAlso Not String.IsNullOrWhiteSpace(pw.Text) Then
If AppLogin.Login(un.Text, pw.Text) Then
SensitiveDataForm.Load()
Close()
Else
Retrys += 1
MessageBox.Show("Login Failed")
End If
Else
MessageBox.Show("Please fill in both username and password")
End If
End Sub
End Class
Public Class ApplicatioLogin
Public Function Login(UserName As String, UserPassword As String) As Boolean
Dim recordCount As Integer
Using cn As New OleDb.OleDbConnection("Your connection string")
Using cmd As New OleDb.OleDbCommand("SELECT Count(*) FROM Users
WHERE UserName = #UserName AND UserPassword = #UserPassword", cn)
cmd.Parameters.Add("#UserName", OleDbType.VarChar).Value = UserName
cmd.Parameters.Add("#UserPassword", OleDbType.VarChar).Value = UserPassword
cn.Open()
recordCount = CInt(cmd.ExecuteScalar)
End Using
End Using
If recordCount = 1 Then
Return True
Else
Return False
End If
End Function
End Class