使用文件流和数据库在 C# 中处理异常

Question

我有这个程序，我必须处理它的异常，但我从来没有做过，所以我有点困惑。我猜我必须处理异常，例如文本文件中的值为空，没有索引，没有“=”或文件为空，但我真的不知道如何定义它们或在哪里把它们。这是我的代码： （文本文件中的行应如下所示： EMPIS_MAG_BUDOW=12

EMPIS_DESKA_FASOLKA=2

SM_PORTAL_POL1=-4 )

    using System;
using FirebirdSql.Data.FirebirdClient;
using System.Collections.Generic;
using System.Linq;
using System.IO;

namespace dokselect
{
    class indexstan
    {
        public string index;
        public double standysp;
    }

    class WynikPorownania
    {
        public string Indeks;
        public int Ilosc;
        public override string ToString()
        {
            return Indeks + " : " + Ilosc;

        }

    }
}
    class Program
    {
        public static void Main()
        {
            ///////CONNECTION

            string conn = "database=C:/PCBiznes/BAZA/IXION2_LOGMAG.FB;user=SYSDBA;password=masterkey;DataSource=192.168.24.112;Port=3050";
            FbConnection myConnection = new FbConnection(conn);
            FbDataReader myReader = null;

            string sql = "select KARTOTEKA.indeks, STANMAG.standysp FROM kartoteka JOIN stanmag using(ID_KARTOTEKA);";
            FbCommand myCommand = new FbCommand(sql, myConnection);

            myConnection.Open();
            myReader = myCommand.ExecuteReader();

            ///////LIST lista1
            List<indexstan> listadb = new List<indexstan>();
            double standysp;
            string index;
            while (myReader.Read())
            {
                index = myReader[0].ToString();
                standysp = Convert.ToDouble(myReader[1]);
                listadb.Add(new indexstan { index=index, standysp=standysp });
                //Console.WriteLine(myReader[0].ToString());
            }
            myConnection.Close();
            Console.WriteLine(listadb.Count);


            //RETURN STANDYSP FUNCTION
            double zwr(string myIndex)
            {
                var result = listadb.FirstOrDefault(listadb => listadb.index == myIndex).standysp;
                return result;
            }
            //zwr("EMPIS_DESKA_FASOLKA");

            //READ FROM TXT AND RETURN HIGHER
            string path = "C:/Users/Praktykant/Documents/textdocs/dok1.txt";
            List<WynikPorownania> listatf = File.ReadAllLines(path).Select(line =>
            {
                var linia = line.Split("=");
                string index = linia[0];
                int value = int.Parse(linia[1]);
                return new WynikPorownania {Indeks = index, Ilosc = (int)Math.Max(value, zwr(index))};
            }).ToList();

            //DISPLAY ALL LISTATF CLASSES
            foreach(object WynikPorownania in listatf)
            {
                Console.WriteLine(WynikPorownania);
            }

        }
    }
}

我尝试过这样的异常，如果没有给出值但它不起作用并且当文本文件中的值为空时程序仍然崩溃

List<WynikPorownania> listatf = File.ReadAllLines(path).Select(line =>
                {
                    var linia = line.Split("=");
                    string index = linia[0];
                    if (linia[1] == "")
                    {
                        throw new Exception("Is empty ... or whatever you caught");
                        return null;
                    }
                    else
                    {
                        int value = int.Parse(linia[1]);
                    }
                

                    return new WynikPorownania { Indeks = index, Ilosc = (int)Math.Max(value, zwr(index)) };
                }).ToList();

Answer 1

要在 C# 中处理异常，您应该使用 try catch（请参阅 c# refence try-catch-finally） 在您的代码中，我建议在 firebird 连接周围包装一个 try catch，因为您依赖于此：

try {
    // your code
} catch (Exception ex) {
    // define what happens if exception is thrown
}

你在 try 中包含例如 firebird 连接和 while 循环的关键，因为这些是你的代码所依赖的东西。

处理文本文件中的值：

//DISPLAY ALL LISTATF CLASSES
// note that I have replaced the "object" with your class.
foreach(WynikPorownania wynikPorownania in listatf)
{
    if (wynikPorownania.Indeks != ... || wynikPorownania.Ilosc != ... )
        throw new Exception("Is empty ... or whatever you caught");
    Console.WriteLine(wynikPorownania);
}

Answer 2

//试试下面的方法。

class Program
{
    public static void Main()
    {
        //CONNECTION
        try
        {
            //... <YOUR CODE>

           //DISPLAY ALL LISTATF CLASSES
           foreach(object WynikPorownania in listatf)
           {
              Console.WriteLine(WynikPorownania);

              /*if <your condition>
              {
                 throw <your exception1>
              }
              else if <your condition>
              {
                throw <your exception1>
              }*/
           }
        
        }   

        catch (Exception <your Exception>)
        {
            // Throw the message 
            // Or return the code
        }
    }
}