ทำหน้า Login เช็คที่ฐานข้อมูลถ้ามี User จริงให้ลิ้งไปหน้าโปรแกรม

Imports System.Data
Imports System.Data.SqlClient

Public Class LoginForm

    Dim conn As New SqlConnection(constr)
    Dim constr As String
    Dim sql As String
    Dim sqldataReader As SqlDataReader
    '  Dim ds As New DataSet
    Dim user As String
    Dim pass As String

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click

        constr = " data source=localhost;database=van_project;integrated security=true"

        With conn
            If .State = ConnectionState.Open Then Close()
            .ConnectionString = constr
            .Open()
            .Close()

        End With
        If Txtuser.Text = "" Then
            MessageBox.Show("ใส่ข้อด้วย", "ไม่มีผู้ใช้", MessageBoxButtons.OK)
        Else
            Readmydata(constr)

        End If
    End Sub

    Public Sub Readmydata(ByVal mycnnstr As String) 'สร้างซับบูลีน

        On Error GoTo 0

        With conn
            If .State = ConnectionState.Open Then Close()
            .ConnectionString = constr
            .Open()
            .Close()


        End With

        sql = " select * from Admins Where Username  = '" & Txtuser.Text & "' and Password = '" & Txtpass.Text & "'"

        Dim sqlcomm As New SqlCommand(sql, conn)
        sqldataReader = sqlcomm.ExecuteReader
        sqldataReader.Read()
        user = sqldataReader.Item("user")
        pass = sqldataReader.Item("pass")
        conn.Close()

        If Txtuser.Text = user And Txtpass.Text = pass Then
            Form1.Show()
            Txtuser.Text = ""
            Txtpass.Text = ""
            Me.Hide()

        Else
            MessageBox.Show("กรุณาใส่ ชื่อและรหัสผ่านให้ถูกต้อง")

        End If

    End Sub

End Class