Ping.SendAsync return 从数据库准备输入时请求空列表

Question

我找到了一个代码来检查多个主机的连接性，它从列表中读取地址并以异步方式 ping 它们并处理结果。

当我使用预定义列表时，例如：

public static List<string> addresses = new List<string> { "172.20.74.1", "192.168.1.103", "192.168.1.104", "192.168.1.105"};

一切正常，但当我从数据库中读取此列表时，出现 NullReferenceException。有人可以帮我解决这个问题吗？

using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.NetworkInformation;
using System.Data.SqlClient;
using System.Collections.Generic;
using System;

namespace asyncPing
{
    class Program
    {
        public static List<string> addresses = getNetAddress();
        //public static List<string> addresses = new List<string> { "172.20.74.1", "192.168.1.103", "192.168.1.104", "192.168.1.105"};
        static void Main(string[] args)
        {
            List<Task<PingReply>> pingTasks = new List<Task<PingReply>>();

            foreach (var address in addresses)
            {
                Console.WriteLine(address);

            }
            foreach (var address in addresses)
            {
                pingTasks.Add(PingAsync(address));
            }

            //Wait for all the tasks to complete
            Task.WaitAll(pingTasks.ToArray());

            //Now you can iterate over your list of pingTasks
            foreach (var pingTask in pingTasks)
            {

                Console.WriteLine(pingTask.Result.Address + "\t" + pingTask.Result.Status);
                if (pingTask.Result.Status != IPStatus.Success)
                {
                    //Do Some Thing
                }
            }
            Console.ReadLine();
        }

        public static List<string> getNetAddress()
        {
            List<string> addr = new List<string>();
            string connetionString = @"Data Source=localhost;Initial Catalog=AlarmsDB;Persist Security Info=True;User ID=sa;Password=123456";



            using (SqlConnection myConnection = new SqlConnection(connetionString))
            {
                //Console.WriteLine("Connection Open  !");
                string oString = "Select ip_address from Networks";
                SqlCommand oCmd = new SqlCommand(oString, myConnection);

                myConnection.Open();
                using (SqlDataReader oReader = oCmd.ExecuteReader())
                {
                    while (oReader.Read())
                    {
                        addr.Add(oReader["ip_address"].ToString());
                    }

                    myConnection.Close();
                }
            }

            return addr;
        }
        static Task<PingReply> PingAsync(string address)
        {
            var tcs = new TaskCompletionSource<PingReply>();
            Ping ping = new Ping();
            ping.PingCompleted += (obj, sender) =>
            {
                tcs.SetResult(sender.Reply);
            };
            ping.SendAsync(address, new object());
            return tcs.Task;
        }
    }
}

行发生异常：

Console.WriteLine(pingTask.Result.Address + "\t" + pingTask.Result.Status);

async pings 方法的结果似乎为空。我不知道为什么当从数据库传递相同的输入时，输出的结果会改变？

Answer 1

感谢大家提出解决问题的建议

2天后终于找到问题的根源

在将 ip 地址传递给 asyncPing 方法之前，我 triming 之后问题解决了。

我把ip地址保存为数据库中的字符串，但不知道为什么我读完后要trim它们

我可以通过更改以下行来解决问题：

using (SqlDataReader oReader = oCmd.ExecuteReader())
                {
                    while (oReader.Read())
                    {                        
                 addr.Add(oReader["ip_address"].ToString().Trim());
                    }

                    myConnection.Close();
                }

Ping.SendAsync return 从数据库准备输入时请求空列表

Ping.SendAsync return empty list request when input prepared from database

c#

asynchronous

ping