如何解决连接已关闭-OleDBConnection错误

问题描述

我通常使用Java，并且仅使用C＃读取旧的MS Access 95数据库，因此我对此并不陌生。 我有一个C＃脚本，可打开一个OleDBConnection到访问数据库并从中读取一些数据：

using System;
using System.Data.OleDb;


namespace ReadMsAccessDB
{
    class Program
    {
        static void Main(string[] args)
        {
            const string connectionString = "Provider = Microsoft.Jet.OLEDB.4.0; Data Source = C:/workspace-csharp/ReadMsAccessDB/ReadMsAccessDB/File/remote.mdb; Persist Security Info = True";
        
            using (var con = new OleDbConnection(connectionString))
            {
                con.OpenAsync();
                var cmd = con.CreateCommand();
                cmd.CommandText = "select * from summary_0199_550";
                cmd.Connection = con;

                using (var dataReader = cmd.ExecuteReader())
                {
                    while (dataReader.Read())
                    {
                        var output = "ScanDateTime: " + dataReader.GetValue(3) + "\n"
                                                        + "RCP_Name: " + dataReader.GetValue(13) + "\n"
                                                        + "Slot: " + dataReader.GetValue(14) + "\n"
                                                        + "DFCT_Tot: " + dataReader.GetValue(19) + "\n"
                                                        + "Area_Count: " + dataReader.GetValue(22) + "\n"
                                                        + "Part1: " + dataReader.GetValue(23) + "\n"
                                                        + "Part2: " + dataReader.GetValue(24) + "\n"
                                                        + "Part3: " + dataReader.GetValue(25) + "\n"
                                                        + "Part4: " + dataReader.GetValue(26) + "\n"
                                                        + "Part5: " + dataReader.GetValue(27) + "\n"
                                                        + "Part6: " + dataReader.GetValue(28) + "\n"
                                                        + "Part7: " + dataReader.GetValue(29) + "\n"
                                                        + "Part8: " + dataReader.GetValue(30) + "\n"
                                                        + "HazeRegion: " + dataReader.GetValue(33) + "\n"
                                                        + "HazeAverage: " + dataReader.GetValue(34) + "\n"
                                                        + "HazePeak: " + dataReader.GetValue(35) + "\n\n";
                        Console.WriteLine(output);
                    }

                }

            }

            Console.ReadLine();
        }
    }
}

该项目是一个控制台应用程序，当我在Debugging上具有配置模式时，在Visual Studio中单击“运行”时，它可以很好地工作。但是，当我尝试在没有调试模式的情况下运行它或发布它并尝试运行.exe文件时，出现连接错误，如下所示：

Unhandled exception. system.invalidOperationException: ExecuteReader requires an open and available Connection. The connection's current state is closed.
at System.Data.OleDb.OleDbConnection.CheckStateOpen(String method)
at System.Data.OleDb.OleDbCommand.ValidateConnection(String method)
at System.Data.OleDb.OleDbCommand.ValidateConnectionAndTransaction(String method)
at System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior,String method)
at System.Data.OleDb.OleDbCommand.ExecuteReader(CommandBehavior behavior)
at ReadMsAccessDB.Program.Main(String[] args) in C:\workspace-csharp\ReadMsAccessDB\ReadMsAccessDB\Program.cs:line 18

我不明白为什么它说关闭连接状态是因为我在使用部分打开了与con.OpenAsync();的连接？

解决方法

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