private void btnLogin_Click(object sender, EventArgs e)
 {
     if (validateLogin())
     {
         if (tbUserName.Text.StartsWith("S"))
         {
             StudentApp frSTudent = new StudentApp();
             frSTudent.studentId = tbUserName.Text.Trim();
             this.Hide();
             frSTudent.ShowDialog();
         }
         else if (tbUserName.Text.StartsWith("T"))
         {
             TeacherApp frTeacher = new TeacherApp();
             frTeacher.teacherId = tbUserName.Text.Trim();
             this.Hide();
             frTeacher.ShowDialog();
         }
         else
         {
             Admin frAdmin = new Admin();
             this.Hide();
             frAdmin.ShowDialog();
         }
     }
 }
        private async void btnSave_Click(object sender, EventArgs e)
        {
            var salf = BCrypt.Net.BCrypt.GenerateSalt(12);
            var pass = BCrypt.Net.BCrypt.HashPassword(tbPassChange.Text.Trim(), salf);

            account.username = studentId;
            account.salf     = salf;
            account.password = pass;

            var jsonAccount = JsonConvert.SerializeObject(account);
            var content     = new StringContent(jsonAccount, Encoding.UTF8, "application/json");
            var result      = await client.PutAsync($@"{pathAccount}/{studentId}", content);

            this.Close();
            MessageBox.Show("Changed Password Successfully", "Message");
            StudentApp frStudent = new StudentApp();

            frStudent.studentId = studentId;
            frStudent.Show();
        }