forms to database connectivity problem

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VB

M doing a project in my college.I created a login page for my software.N its working too.But when i change username and password in database ,its not working..moreover when i leave any one of the fields empty it has to give a error msg about that particular field..eg:passsword is emptyCan u help me plz!!
here is my code:

Imports System.Data
Imports System.Data.SqlClient
Public Class login1

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        TextBox1.Text = ""
        TextBox2.Text = ""


    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If (ComboBox1.Text = "select") Then
            MessageBox.Show("please select user or admin")
            TextBox1.Text = ""
            TextBox2.Text = ""

        End If

        Try

            If (ComboBox1.Text = "admin") Then
                Dim str As String = "select * from log where adm = 'admin'; "
                Dim con As New SqlConnection()
                con.ConnectionString = "Data Source=PROJECT-856F221\SQLEXPRESS;Initial Catalog=farma;Integrated Security=True"
                con.Open()
                Dim cmd As New SqlCommand(str, con)
                Dim reader As SqlDataReader
                reader = cmd.ExecuteReader
                Dim found As Integer = 0
                Dim un, pwd, un1, pwd1, grp, grp1 As String
                grp = ComboBox1.Text.Trim()
                un = TextBox1.Text.Trim()
                pwd = TextBox1.Text.Trim()
                While (reader.Read())
                    grp1 = reader.GetString(0).Trim()
                    un1 = reader.GetString(1).Trim()
                    pwd1 = reader.GetString(2).Trim()
                    If (grp = grp1 And un = un1 And pwd = pwd1) Then
                        found = 1
                        Exit While
                    End If
                End While
                reader.Close()
                con.Close()
                If found = 0 Then
                    Label3.Visible = True
                    Label3.Text = "User Name or Password Incorrect"
                Else
                    adminhom.Show()
                    Me.Hide()


                End If
            ElseIf (ComboBox1.Text = "user") Then
                user_login()
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub
    Sub user_login()
        Try

            Dim str As String = "select * from log where adm = 'user'"
            Dim con As New SqlConnection()
            con.ConnectionString = "Data Source=PROJECT-856F221\SQLEXPRESS;Initial Catalog=farma;Integrated Security=True"
            con.Open()
            Dim cmd As New SqlCommand(str, con)
            Dim reader As SqlDataReader
            reader = cmd.ExecuteReader
            Dim found As Integer = 0
            Dim un, pwd, un1, pwd1 As String
            un = TextBox1.Text.Trim()
            pwd = TextBox1.Text.Trim()
            While (reader.Read())
                un1 = reader.GetString(1).Trim()
                pwd1 = reader.GetString(2).Trim()
                If (un = un1 And pwd = pwd1) Then
                    found = 1
                    Exit While
                End If
            End While
            reader.Close()
            con.Close()
            If found = 0 Then
                Label3.Visible = True
                Label3.Text = "User Name or Password Incorrect"
            Else
                farmerhome.Show()
                Me.Hide()


            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message)

        End Try
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Label3.Visible = False

    End Sub


    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged

    End Sub

    Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox2.TextChanged

    End Sub

    Private Sub Label3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label3.Click

    End Sub
End Class