private void Clear()
{
selectedTest = null;
tbName.Text = "";
tbPassMark.Text = "";
buttonUpdate.Enabled = false;
buttonDelete.Enabled = false;
}
private void dataGridView1_CellMouseDoubleClick(object sender, DataGridViewCellMouseEventArgs e)
{
int idTest = Int32.Parse(dataGridView1["id", e.RowIndex].Value.ToString());
selectedTest = tests.Find(item => item.id.Equals(idTest));
tbName.Text = selectedTest.Name.Trim();
tbPassMark.Text = selectedTest.PassMark.ToString();
buttonUpdate.Enabled = true;
buttonDelete.Enabled = true;
}