private void button1_Click(object sender, EventArgs e) { int num = Convert.ToInt32(textBox3.Text); bok = LibraryDB.GetBooks(num); if (bok == null) { MessageBox.Show("The book has not been found"); } else { button3.Enabled = true; button5.Enabled = true; this.DisplayBooks(); } OleDbConnection conn = LibraryDB.GetConnection(); DataTable dt = new DataTable(); OleDbDataAdapter adapter = new OleDbDataAdapter("select * from Books Where (BookID=@id)", conn); adapter.SelectCommand.Parameters.AddWithValue("@bookid", textBox3.Text); adapter.Fill(dt); dataGridView1.DataSource = dt; }