c# - 如何在while循环中将数据读取器中的值传递给C#中的方法

Question

我在使用 SQL 语句迭代的数据库中有 3 个表。它搜索需要续签合同的应用程序。我使用 SQL 日期数学来检查是否需要通知经理续签合同。如果今天的日期 = notificationDate 字段中的日期，则控制台应用程序应向列为该应用程序的分析师/经理的人发送电子邮件。到目前为止，这是我的代码：

namespace ContractApp
{
    class Program
    {
        //initializes strings for storing information from the table
        static string aretheyManager;
        static string listedanalystEmail;
        static string listedmanagerEmail;

    static void Main(string[] args)
    {
        int warningWindow = 10;

        try
        {
            //connects to the AppInfo_dev table in the database
            SqlConnection conn = new SqlConnection("server=10.52.2.169\\sqlcluster,1206;uid=TannerAppsWriter;pwd=TannerAppsWriter;database=AppInfo_dev;");
            conn.Open();

            //sets up a sequal command called selectedValues
            SqlCommand selectValues = conn.CreateCommand();

            //Pulls information from three tables in the database (AppInfo_dev, SoftwareApp, IT_Personnel)
            //Takes the AppID from the Contracts list and compares it to AppID in the Apps list and displays matches
            //Then it finds employee information related to the Primary Analyst that is listed for that application
            //Adds a field called "notificationDate" that is filled by subtracting the "warningWindow" and "TerminationWindow" from the RenewalDate
            //Finds contracts listed that have a "notificationDate" that is the same as the current date
            //Takes the eMail fields and appends "@tanner.org" to the end of the text in the field
            selectValues.CommandText = "My SQL statement goes here...it works so I didn't bother posting it since it is really long"

            //Reads values in specified columns in the database
            using (SqlDataReader dataReader = selectValues.ExecuteReader())
            {
                if (dataReader.HasRows)
                {
                    while (dataReader.Read())
                    {
                        //Converts the values in the tables to strings
                        aretheyManager = Convert.ToString(dataReader["isManager"]);
                        listedanalystEmail = Convert.ToString(dataReader["analystEmail"]);
                        listedmanagerEmail = Convert.ToString(dataReader["managerEmail"]);
                    }
                }
            }
        }
        //If there is an error, catch it
        catch (SqlException e)
        {
        Console.WriteLine(e.Message);
        }
    }

    private void sendEmailNotification()
    {


        //Create an email to send notifying of contract termination
        MailMessage message = new MailMessage();

        //Check to see if the listed analyst is a manager
        //If they are, send the email to them
        //If they are not, send they email to their manager.
        if (aretheyManager == "True")
        {
            message.To.Add(listedanalystEmail);
        }
        else
        {
            message.To.Add(listedmanagerEmail);
        }

        message.Subject = "This contract requires your attention!";
        message.From = new MailAddress("no response email address goes here");
        message.Body = "There is an application contract that is in need of renewal.";

        message.Priority = MailPriority.Normal;

        SmtpClient client = new SmtpClient("client info goes here");
        client.Send(message);
    }
}

}

SQL 语句按预期工作。它遍历表中的行并使用 notificationDate = 当前日期提取合同。我在使用数据读取器时遇到问题。它遍历由 SQL 语句提取的合约，但仅将它读取的最后一个值存储到字符串中。我需要它来存储它提取的所有值，以便在需要通知多个人时向每个人发送一封电子邮件。

score 2 · Accepted Answer

您正在循环 dataSet 但将值存储在字符串而不是某种列表中。这就是为什么只存储最后一个值

  //create a class to hold the value
class SomeDTO
{
   public string aretheyManager;
   public string listedanalystEmail;
   public string listedmanagerEmail;
}
  //in your main
 //Reads values in specified columns in the database
            List<SomeDTO> collection = new List<SomeDTO>();
            using (SqlDataReader dataReader = selectValues.ExecuteReader())
            {
                if (dataReader.HasRows)
                {
                    while (dataReader.Read())
                    {
                       SomeDTO obj = new SomeDTO();
                        //Converts the values in the tables to strings
                        obj.aretheyManager = Convert.ToString(dataReader["isManager"]);
                        obj.listedanalystEmail = Convert.ToString(dataReader["analystEmail"]);
                        obj.listedmanagerEmail = Convert.ToString(dataReader["managerEmail"]);

                       collection.Add(obj);

                    }
                }
                dataReader.Close();
                dataReader.Dispose();
            }


//send email notification method
private void sendEmailNotification(List<SomeDTO> obj)
{
     //loop and send email
}

score 2 · Accepted Answer

数据读取器不是为保存数据而设计的。它只是迭代数据。如果您想存储“读取”的结果，请将数据添加到 ArrayList 或其他允许您对数据执行进一步工作的数据结构中。

 con.Open();

    ArrayList al = new ArrayList();
    SqlDataReader dr = cmd.ExecuteReader();

    while(dr.Read()) {
        object[] values = new object[dr.FieldCount];
        dr.GetValues(values);
        al.Add(values);
    }

    dr.Close();
    con.Close();

score 1 · Accepted Answer

首先将您的 SendMail 方法更改为更通用。
接收包含应接收邮件的人员信息的参数

private void sendEmailNotification(string aretheyManager, 
                                  string listedanalystEmail, 
                                  string listedmanagerEmail)
{
    //Create an email to send notifying of contract termination
    MailMessage message = new MailMessage();

    //Check to see if the listed analyst is a manager
    //If they are, send the email to them
    //If they are not, send they email to their manager.
    if (aretheyManager == "True")
    {
        message.To.Add(listedanalystEmail);
    }
    else
    {
        message.To.Add(listedmanagerEmail);
    }

    message.Subject = "This contract requires your attention!";
    message.From = new MailAddress("no response email address goes here");
    message.Body = "There is an application contract that is in need of renewal.";

    message.Priority = MailPriority.Normal;

    SmtpClient client = new SmtpClient("client info goes here");
    client.Send(message);
}

现在在您的循环中，当您从阅读器读取数据时，调用上述方法传递适当的值

    if (dataReader.HasRows)
    {
        while (dataReader.Read())
        {
            //Converts the values in the tables to strings
            aretheyManager = Convert.ToString(dataReader["isManager"]);
            listedanalystEmail = Convert.ToString(dataReader["analystEmail"]);
            listedmanagerEmail = Convert.ToString(dataReader["managerEmail"]);

            // For every record read, send the email
            sendEmailNotification(aretheyManager, 
                                  listedanalistEmail, 
                                  listedmanagerEmail)                        
        }
    }

当然，您也可以将从 DataReader 检索到的值存储在某种形式的对象集合中（List<Email>其中 EMail 是一个包含您的三个参数的类），但这将导致双循环（一个用于读取，一个用于发送电子邮件）因此，如果真的不需要将所有这些电子邮件地址存储在内存中，我建议您在阅读阅读器时发送邮件。

score 0 · Accepted Answer

       using (var reader = selectValues.ExecuteReader()) {
           return reader.Cast<IDataRecord>()
                        .Select(record => new SomeDTO {
                                  aretheyManager = Convert.ToString(record["isManager"]),
                                  listedanalystEmail = Convert.ToString(record["analystEmail"]),
                                  listedmanagerEmail = Convert.ToString(record["managerEmail"])
                               })
                        .ToList();
       }

score 0 · Accepted Answer

一种解决方案是创建一个Person类

public class Person
{
    public bool IsManager { get; set; }
    public string AnalystEmail { get; set; }
    public string ManagerEmail { get; set; }
}

然后在你的Program课堂上你需要声明一个List<Person> _personList = new List<Person>();

最后，在你的while loop：

while (dataReader.Read())
{
    _personList.Add(new Person {
        IsManager = Convert.ToBool(dataReader["isManager"]),
        AnalystEmail = Convert.ToString(dataReader["analystEmail"]),
        ManagerEmail = Convert.ToString(dataReader["managerEmail"])
    });
}

之后，您可以使用foreach(var person in _personList)或类似的方式发送电子邮件。

score 0 · Accepted Answer

无论您迭代这些值多少次，每次都会更新您的值，并且您只会获得最后更新的值。因为对于每次迭代，您都在为您的strings.

               while (dataReader.Read())
                {
                    //Converts the values in the tables to strings
                    aretheyManager = Convert.ToString(dataReader["isManager"]);
                    listedanalystEmail = Convert.ToString(dataReader["analystEmail"]);
                    listedmanagerEmail = Convert.ToString(dataReader["managerEmail"]);
                }

我认为您应该使用某种集合来存储您的值。

          List<string> aretheyManager = new List<string>(); 
          List<string> listedanalystEmail =new List<string>();  
         List<string> listedmanagerEmail = new List<string>();  


        while (dataReader.Read())
                {
                //Converts the values in the tables to strings
               aretheyManager.Add(Convert.ToString(dataReader["isManager"]));
               listedanalystEmail.Add( Convert.ToString(dataReader["analystEmail"]));
               listedmanagerEmail.Add(Convert.ToString(dataReader["managerEmail"]));
                }

score -1 · Accepted Answer

创建一个struct来保存您的所有详细信息，然后创建一个List<yourstruct>.

struct在你的循环中填充你的。

当您退出循环时，调用您的电子邮件方法并传递列表。

在您的电子邮件方法foreach中，您的列表每次发送电子邮件

c# - 如何在while循环中将数据读取器中的值传递给C#中的方法

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