find max in a table column

https://www.codeproject.com/Questions/691857/How-to-get-max-value-of-a-column-in-datatable


   DataSet ds = new DataSet();
            SqlDataAdapter adapter = new SqlDataAdapter();
            //get all the tables from market data database
            //String q1 = "SELECT name FROM market_data.sys.Tables where name not like '%_dss%' and name not like 'tick';";
            //String q1 = "SELECT * FROM [market_data].[dbo].[" + txtSym.Text + "];";
            string q1 = "SELECT top (20) [Volume] ,[Open],[High],[Low],[Close],[WAP],[Count],[dt],[EMA9],[EMA10],[EMA20],[EMA21],[EMA50],[EMA100],[EMA200] FROM [market_data].[dbo].[" + txtSym.Text + "];";
            SqlCommand cmd = new SqlCommand(q1, cnn);
            adapter.SelectCommand = cmd;

            //Retrieve the records from database
            adapter.Fill(ds);

            DataRow[] result = ds.Tables[0].Select("Close = MAX(Close)");
            double max = Convert.ToDouble(result[0][4].ToString()) + 5.00;

            chart1.Series["Series1"].ChartType = SeriesChartType.Candlestick;
         
            chart1.DataSource = ds;