c# – 为什么这个循环不循环？

2023年7月17日 185次阅读 
string GetSerials = "SELECT SerialNumber from Warranty";
            string TestUpdateDates = "UPDATE Warranty SET StartDate = '@StartDate', EndDate = '@EndDate' WHERE SerialNumber = '@result'";
            //string TestUpdateDates2 = "UPDATE Warranty SET StartDate = cDate(Format('@StartDate', 'MM/dd/yyyy')), EndDate = cDate(Format('@EndDate', 'MM/dd/yyyy')) WHERE(SerialNumber = '@result')";

DataTable dataTable = new DataTable();
  using (var conn1 = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Blah\Blah\Blah\Warranty.accdb"))
  using (OleDbCommand serialCommand = new OleDbCommand(GetSerials, conn1))
  {
    conn1.Open();
    dataTable.Load(serialCommand.ExecuteReader());

    foreach (DataRow row in dataTable.Rows)
    {
      var result = row["SerialNumber"].ToString();
      WebRequest request = WebRequest.Create("urlpart1" + result + "urlpart2");
      string json;
      var response = request.GetResponse();
      request.ContentType = "application/json; charset=utf-8";

      using (var streamr = new StreamReader(response.GetResponseStream()))
      using (OleDbCommand testupdateCommand = new OleDbCommand(TestUpdateDates, conn1))
      using (OleDbCommand updateCommand = new OleDbCommand(UpdateDates, conn1))
      using (OleDbCommand deleteCommand = new OleDbCommand(DeleteIncomplete, conn1))
      {
        json = streamr.ReadToEnd();
        List<MyObject> list = JsonConvert.DeserializeObject<List<MyObject>>(json);
        MyObject obj = list[0]; //Base Warranty

        // obj -- Base Warranty
        var StartDate = obj.Start;
        var EndDate = obj.End;

        //testupdateCommand.Parameters.Add("@StartDate", OleDbType.Date).Value = StartDate;
        //testupdateCommand.Parameters.Add("@EndDate", OleDbType.Date).Value = EndDate;
        testupdateCommand.Parameters.AddWithValue("@StartDate", StartDate);
        testupdateCommand.Parameters.AddWithValue("@EndDate", EndDate);
        testupdateCommand.Parameters.AddWithValue("@result", result);

我正在尝试使用JSON响应中的值更新我的数据库.我想遍历列[“SerialNumber”]中的所有值并使用该序列号,我可以从URL获取开始日期和结束日期.我想将这些值存储到相同的序列号中,我将其用于将url放入相应的字段(StartDate,EndDate).

我已经注释了我试图做的其他一些方法,但我得到的输出是只有我得到的第一个SerialNumber被更改,它不会继续循环我的列100个值.如果我加

MessageBox.Show(result); //SerialNumber
MessageBox.Show(StartDate.ToString());
MessageBox.Show(EndDate.ToString());

它通过MessageBox.Show循环,但它不会以这种方式更新我的数据库.为什么不自己迭代？

我正在使用ACCESS2013如果这很重要

最佳答案 不要引用参数:)

string GetSerials = "SELECT SerialNumber from Warranty";
                string TestUpdateDates = "UPDATE Warranty SET StartDate = @StartDate, EndDate = @EndDate WHERE SerialNumber = @result";
                //string TestUpdateDates2 = "UPDATE Warranty SET StartDate = cDate(Format(@StartDate, 'MM/dd/yyyy')), EndDate = cDate(Format(@EndDate, 'MM/dd/yyyy')) WHERE(SerialNumber = @result)";

    DataTable dataTable = new DataTable();
      using (var conn1 = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Blah\Blah\Blah\Warranty.accdb"))
      using (OleDbCommand serialCommand = new OleDbCommand(GetSerials, conn1))
      {
        conn1.Open();
        dataTable.Load(serialCommand.ExecuteReader());

        foreach (DataRow row in dataTable.Rows)
        {
          var result = row["SerialNumber"].ToString();
          WebRequest request = WebRequest.Create("urlpart1" + result + "urlpart2");
          string json;
          var response = request.GetResponse();
          request.ContentType = "application/json; charset=utf-8";

          using (var streamr = new StreamReader(response.GetResponseStream()))
          using (OleDbCommand testupdateCommand = new OleDbCommand(TestUpdateDates, conn1))
          using (OleDbCommand updateCommand = new OleDbCommand(UpdateDates, conn1))
          using (OleDbCommand deleteCommand = new OleDbCommand(DeleteIncomplete, conn1))
          {
            json = streamr.ReadToEnd();
            List<MyObject> list = JsonConvert.DeserializeObject<List<MyObject>>(json);
            MyObject obj = list[0]; //Base Warranty

            // obj -- Base Warranty
            var StartDate = obj.Start;
            var EndDate = obj.End;

            //testupdateCommand.Parameters.Add("@StartDate", OleDbType.Date).Value = StartDate;
            //testupdateCommand.Parameters.Add("@EndDate", OleDbType.Date).Value = EndDate;
            testupdateCommand.Parameters.AddWithValue("@StartDate", StartDate);
            testupdateCommand.Parameters.AddWithValue("@EndDate", EndDate);
            testupdateCommand.Parameters.AddWithValue("@result", result);
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