Forgot password using mail

Protected Sub Button4_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button4.Click
Dim mailtxt As String = mail_txt.Text
Dim numtxt As String = num_txt.Text
Dim sbmail As New StringBuilder
Dim conn As New MySqlConnection("DataBase=sample;Data source=localhost;username=root;password=sa;")
Dim str As String
str = " select * from user_details where email='" + mail_txt.Text + "' and secno='" + num_txt.Text + "' "
Dim cmd As New MySqlCommand(str, conn)
conn.Open()
Dim dr As MySqlDataReader = cmd.ExecuteReader()
dr.Read()
Dim userID As New Integer
If dr.HasRows Then
Dim dbuname As String = dr("user_name").ToString()
Dim dbpassword As String = dr("user_password").ToString()
Dim dbemail As String = dr("email").ToString()
Dim dbnum As String = dr("secno").ToString()

If ((String.Equals(mailtxt, dbemail)) And (String.Equals(numtxt, dbnum))) Then
Dim MailMsg As New MailMessage()
MailMsg.To.Add("mail_txt.Text".ToString())
MailMsg.From = New MailAddress("anub96@gmail.com")
MailMsg.Subject = "Retrive Your Password"
Dim body As String = ("username=" + dbuname + " " + "password=" + dbpassword + " " + "mailid=" + dbemail + " ")
MailMsg.Body = body.ToString()
MailMsg.IsBodyHtml = True
Dim SmtpMail As New SmtpClient()
SmtpMail.Host = "smtp.gmail.com"
SmtpMail.Port = 587
SmtpMail.Credentials = New System.Net.NetworkCredential("anub96", "capricorn")
SmtpMail.EnableSsl = True
SmtpMail.Send(MailMsg)
End If

Else
Response.Write("<script> Window.Alert('Invalid User')</script>")
End If
End Sub