C# DataTable

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Ringo
{
public partial class Form_1009 : Form
{
DataSet_1009 ds = null;
DataSet_1009 fds = null;
DataSet_1009 Finalds = null;

    public Form_1009()
    {
        Init();

        InitCalc();

        Calc();

        InitializeComponent();
    }


    private void Init()
    {
        ds = new DataSet_1009();
        fds = new DataSet_1009();
        Finalds = new DataSet_1009();

        for (int i = 1; i <= 3; i++)
        {
            DataSet_1009.T_DtRow tRow = fds.T_Dt.NewT_DtRow();
            tRow.T_id = "2022/02/0" + (i + 2).ToString();
            tRow.T_data = "test_" + (i + 2).ToString();
            fds.T_Dt.Rows.Add(tRow);

            DataSet_1009.T_DtRow tttRow = fds.T_Dt.NewT_DtRow();
            tttRow.T_id = "2022/02/0" + (i + 2).ToString();
            tttRow.T_data = "test_" + (i + 2).ToString();
            fds.T_Dt.Rows.Add(tttRow);
        }

        DataSet_1009.T_DtRow ttRow = fds.T_Dt.NewT_DtRow();
        ttRow.T_id = "2022/02/08";
        ttRow.T_data = "test_8";
        fds.T_Dt.Rows.Add(ttRow);

        for (int i = 1; i <= 9; i++)
        {
            DataSet_1009.F_DtRow dayRow = ds.F_Dt.NewF_DtRow();
            dayRow.D_id = "2022/02/0" + i.ToString();
            dayRow.D_data = "test_" + i.ToString();
            ds.F_Dt.Rows.Add(dayRow);

            DataSet_1009.F_DtRow stayRow = ds.F_Dt.NewF_DtRow();
            stayRow.S_id = "2022/02/0" + i.ToString();
            stayRow.S_data = "test_" + i.ToString();
            ds.F_Dt.Rows.Add(stayRow);

        }
    }


    private void InitCalc()
    {
        string preDay = string.Empty;
        string day_id = string.Empty;
        string day_data = string.Empty;
        string stay_id = string.Empty;
        string stay_data = string.Empty;
        for (int i = 0; i < ds.F_Dt.Rows.Count; i++)
        {
            day_id = ds.F_Dt.Rows[i]["D_id"].ToString();
            if (!string.IsNullOrEmpty(day_id))
            {
                preDay = day_id;
            }
            day_data = ds.F_Dt.Rows[i]["D_data"].ToString();

            // 「ds.T_Dt」に「D/S」をまとめる。
            if (!string.IsNullOrEmpty(day_id))
            {
                DataSet_1009.T_DtRow ttRow = ds.T_Dt.NewT_DtRow();
                ttRow.D_id = day_id;
                ttRow.D_data = day_data;
                ds.T_Dt.Rows.Add(ttRow);
            }

            // Sも同じレコードか？
            if (i + 1 <= ds.F_Dt.Count - 1)
            {
                stay_id = ds.F_Dt.Rows[i + 1]["S_id"].ToString();
                stay_data = ds.F_Dt.Rows[i + 1]["S_data"].ToString();
                if (!string.IsNullOrEmpty(stay_id))
                {
                    if (preDay.Equals(stay_id))
                    {
                        // Edit
                        int rowNo = ds.T_Dt.Count - 1;
                        ds.T_Dt.Rows[rowNo]["S_id"] = stay_id;
                        ds.T_Dt.Rows[rowNo]["S_data"] = stay_data;
                    }
                    else
                    {
                        // Add(insertAt)
                        int rowNo = ds.T_Dt.Count - 1;
                        DataSet_1009.T_DtRow tRow = ds.T_Dt.NewT_DtRow();
                        ds.T_Dt.Rows.InsertAt(tRow, rowNo);
                    }
                }
            }

            //var T_01 = fds.T_Dt.Select("T_id = '" + day_id + "'", "T_data");
            //var T_02 = fds.T_Dt.Select("T_id = '" + stay_id + "'", "T_data");
        }
    }


    private void Calc()
    {
        //ds.T_Dt
        string date = string.Empty;
        var dsDr = ds.T_Dt.Rows;
        for (int i = 0; i < dsDr.Count; i++)
        {
            date = dsDr[i]["D_id"].ToString();

            var fds_dataRow = fds.T_Dt.Select("T_id = '" + date + "'", "T_data");
            for(int j = 0; j < fds_dataRow.Length; j++)
            {
                DataSet_1009.T_DtRow tRow = Finalds.T_Dt.NewT_DtRow();
                tRow.T_id = fds_dataRow[j]["T_id"].ToString();
                tRow.T_data = fds_dataRow[j]["T_data"].ToString();
                Finalds.T_Dt.Rows.Add(tRow);
            }

            // Add
            DataSet_1009.T_DtRow ttRow = Finalds.T_Dt.NewT_DtRow();
            ttRow.D_id = dsDr[i]["D_id"].ToString();
            ttRow.D_data = dsDr[i]["D_data"].ToString();
            ttRow.S_id = dsDr[i]["S_id"].ToString();
            ttRow.S_data = dsDr[i]["S_data"].ToString();
            Finalds.T_Dt.Rows.Add(ttRow);
        }

        //fds.T_Dt
        //    ds.T_Dt
        //Finalds


    }
}

}