C#：DataTable 操作

DataTable 的創建，列名讀取，文本格式化

namespace MyTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Test();
        }        
        private static void Test()
        {
            //創建一個表
            DataTable dt = new DataTable("Product");
            DataColumn dc = null;

            //添加列，賦值
            dc = dt.Columns.Add("id", Type.GetType("System.Int32"));
            dc.AutoIncrement = true;
            dc.AutoIncrementSeed = 1;
            dc.AutoIncrementStep = 1;
            dc.AllowDBNull = false;
            dt.Columns.Add("pname", Type.GetType("System.String"));
            dt.Columns.Add("price", Type.GetType("System.Double"));
            dt.Columns.Add("memo", Type.GetType("System.String"));

            DataRow dr = dt.NewRow();
            dr["pname"] = "red apple";
            dr["price"] = 9.9;
            dr["memo"] = "this red apple so red.";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["pname"] = "black apple";
            dr["price"] = 19.9;
            dr["memo"] = "this black apple so black.";
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["pname"] = "gold apple";
            dr["price"] = 29.9;
            dr["memo"] = "this gold apple so gold.";
            dt.Rows.Add(dr);

            //取列名
            List<string> cnameList = new List<string>();
            foreach(DataColumn dcn in dt.Columns)
            {
                cnameList.Add(dcn.ColumnName);
                Console.Write($"{String.Format("{0,-12}", dcn.ColumnName)}");  //執行結果：（例）"red apple   ",占12位,向左對齊
            }
            Console.WriteLine("\t\n");
            //根據列名來讀取行數據
            foreach(DataRow row in dt.Rows)
            {
                foreach(string cname in cnameList)
                {
                    string args = row[cname].ToString();                    
                    if(args.Length>12)
                    {
                        Console.Write($"{args}");
                    }
                    else
                    {
                        Console.Write($"{String.Format("{0, -12}", args)}");
                    }
                }
                Console.WriteLine("\n");
            }
        }
    }
}

執行結果：