private void delete__Click(object sender, EventArgs e)
{
int curruentRow = dataGridView1.CurrentCell.RowIndex;
DataGridViewRow selectedRow = dataGridView1.Rows[curruentRow];
dataGridView1.Rows.Remove(dataGridView1.Rows[curruentRow]);
Student.delete_student(curruentRow);
//MessageBox.Show(curruentRow.ToString());
}