private void btnUpdate_Click(object sender, EventArgs e)
    {
        try
        {
            if (txtOgrenciNo.Text.Length != 0 && txtAd.Text.Length != 0 && txtSoyad.Text.Length != 0 && txtEmail.Text.Length != 0 && txtTelefon.Text.Length != 0)
            {
                string query ="UPDATE ogrenci(studentId,name,lname,email,phone) SET (studentId=@studentId,name@name,lname=@lname,email=@email,phone=@phone)";
                string query1 = "UPDATE loginusers(username,upassword) SET (username=@email,upassword=@phone)";
                using (connection = new SqlConnection(connectionString))
                using (SqlCommand command = new SqlCommand(query, connection))
                using (SqlCommand cmd = new SqlCommand(query1, connection))
                {
                    connection.Open();
                    cmd.Parameters.AddWithValue("@emailVal", txtEmail.Text);
                    cmd.Parameters.AddWithValue("@phone", txtPhone.Text);
                    command.Parameters.AddWithValue("@studentId", txtStudentId.Text);
                    command.Parameters.AddWithValue("@name", txtName.Text);
                    command.Parameters.AddWithValue("@lname", txtLname.Text);
                    command.Parameters.AddWithValue("@email", txtEmail.Text);
                    command.Parameters.AddWithValue("@phone", txtPhone.Text);
                    cmd.ExecuteNonQuery();
                    command.ExecuteNonQuery();
                    populateGrid();
                }
            }
            else
            {
                MessageBox.Show("Student Information can not be blank","Alert",MessageBoxButtons.OK,MessageBoxIcon.Information);
            }
        }
        catch (Exception)
        {
            MessageBox.Show("Please enter different student info", "Alert", MessageBoxButtons.OK, MessageBoxIcon.Information);
        }
    }