DEMOP, C# - rextester

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using Dapper;

namespace PTT {
   public partial class Demo : Form {
      public Demo() {
         InitializeComponent();
      }
      private string mySqlConn = "Server=localhost;Database=ppt_c_sharp;Uid=root;Pwd=1111;";

//建立物件模型
      public class DemoModel
      {
         public string Id { get; set; }
         public int Number { get; set; }
      }

private void Form1_Load(object sender,EventArgs e) {
        
         var mySqlConnection = new MySql.Data.MySqlClient.MySqlConnection(mySqlConn);
         using(mySqlConnection) {
            string mySqlCmd = "select * from demo";
            
            //Dapper取得資料並對應物件模型
            List<DemoModel> results = mySqlConnection.Query<DemoModel>(mySqlCmd).ToList();
            
            //IEnumerable自己就有sum method.下Linq也沒問題
            sumResult.Text = results.Sum(c => c.Number).ToString();
            avgResult.Text = results.Average(c => c.Number).ToString();
            
            //DataGridView本身就可以接強型別
            //dataResult.DataSource = results;

//要直接加在GridView裡面也ok
            results.Add(new DemoModel(){Id="合計",Number = results.Sum(c=>c.Number)});
            dataResult.DataSource = results;

}

}
   }
}

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