一个很好的Demo

using System;
using System.Data;
using System.Data.SqlClient;

namespace Demo3
{
    /// <summary>
    /// Class1 的摘要说明。
    /// </summary>
    class Class1
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            //
            // TODO: 在此处添加代码以启动应用程序
            Demo dm = new Demo();
            dm.DoDemo();
            //
        }
    }
    class Demo
    {
        public void DoDemo()
        {
            DataSet ds = new DataSet();
            ExecuteOptions oExecute = new ExecuteOptions();
            ds = oExecute.ExecuteandFill();
            //Display all sales transactions on the console
            
            //An action query doesnt generate any results for processing
            oExecute.ExecuteNonQuery();

            //Use the reader to walkthrough the results in a forward-only manner
            oExecute.ExecuteReader();
            
            //Return the total number of sale transactions in the database
            int nSum=oExecute.ExecuteScalar();
            Console.WriteLine("Record count is " +nSum.ToString());
            
        }
    }
    class ExecuteOptions
    {
        public SqlDataReader ExecuteReader()
        {
            SqlConnection con = new SqlConnection("Server=localhost; Integrated Security=SSPI; database=mydatabase; Max Pool Size=75; Min Pool Size=5");
            SqlCommand cmdTitle = new SqlCommand("select Username,password,score from scoretable",con);
            cmdTitle.CommandType=CommandType.Text;

            SqlDataReader dr;
            con.Open();
            dr =cmdTitle.ExecuteReader(CommandBehavior.CloseConnection);
            return dr;
        }
        public int ExecuteScalar()
        {
            SqlConnection con = new SqlConnection("Server=localhost; Integrated Security=SSPI; database=mydatabase;Max Pool Size=75; Min Pool Size=5");
            SqlCommand cmdTitleCount = new SqlCommand("select count(*) from scoretable",con);
            cmdTitleCount.CommandType=CommandType.Text;
            con.Open();
            return Convert.ToInt32(cmdTitleCount.ExecuteScalar().ToString());
        }
        public void ExecuteNonQuery()
        {
            SqlConnection con = new SqlConnection("Server=localhost; Integrated Security=SSPI; database=mydatabase;Max Pool Size=75; Min Pool Size=5");
            SqlCommand cmdUpdateSales = new SqlCommand("Update scoretable set score = score+200 where username='成龙'",con);
            cmdUpdateSales.CommandType=CommandType.Text;
            con.Open();
            cmdUpdateSales.ExecuteNonQuery();
        }
        public DataSet ExecuteandFill()
        {
            SqlConnection con = new SqlConnection("Server=localhost; Integrated Security=SSPI; database=mydatabase;Max Pool Size=75; Min Pool Size=5");
            SqlDataAdapter da = new SqlDataAdapter("select username, password,score from scoretable",con);
            DataSet ds = new DataSet();
            con.Open();
            da.Fill(ds);
            return ds;
        }
    }


}