试试这个

try this

private void dataGridView1_CellClick_1(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == dataGridView1.Columns["Column2"].Index && e.RowIndex >= 0)
            {
                //MessageBox.Show(dataGridView1.Rows[e.RowIndex].Cells[0].Value.ToString());
                OleDbConnection con=new OleDbConnection("YourConnectionString");
                string str = "select * course from YourTableName where room='" + dataGridView1.Rows[e.RowIndex].Cells[0].Value.ToString() + "'";
                OleDbCommand cmd = new OleDbCommand(str, con);
                OleDbDataReader dr = cmd.ExecuteReader();
                if (dr.HasRows)
                {
                    dr.Read();
                    MessageBox.Show(dr[0].ToString());
                }

            }
        }