tady je kod do VB

Imports MySql.Data.MySqlClient
Imports System.Data



form1.load code:



Dim conn As MySqlConnection
'connect to DB
conn = New MySqlConnection()
conn.ConnectionString = "server=localhost; user id=myroot; password=mypwd; database=login"
'see if connection failed.
Try
conn.Open()
Catch myerror As MySqlException
MessageBox.Show("Error Connecting to Database: " & myerror.Message)
End Try





login button code:



'sql query
Dim myAdapter As New MySqlDataAdapter

Dim sqlquery = "SELECT username, password FROM userlist Where username='" & UsernameTextBox.Text & "' and password='" & PasswordTextBox.Text & "'"
Dim myCommand As New MySqlCommand()
myCommand.Connection = conn
myCommand.CommandText = sqlquery
'start query
myAdapter.SelectCommand = myCommand
Dim myData As MySqlDataReader
myData = myCommand.ExecuteReader()
'see if user exits.
If myData.HasRows = 0 Then
MessageBox.Show("Invalid Login Details", "Login Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
Dim frm1 = New Form1
Frm1.Show()
Me.Visible = False
End If



last code:





Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
LoginForm1.Visible = True
End Sub