I had to switch my code from being in .NET Core to .NET Framework and now I get an error. the error says that local variable named 'listadb' cannot be declared in this scope. This function worked before and I don't know how to get around it now. Here is the code:

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;
    }

    public class WynikPorownania
    {
        public string Indeks;
        public int Ilosc;
        public override string ToString()
        {
            return Indeks   " : "   Ilosc;
        }
    }
    class Program
    {
        public static List<WynikPorownania> funkcjalista()
        {
            ///////CONNECTION
                string conn = "CONNECTION STRING";
                FbConnection myConnection = new FbConnection(conn);
                FbDataReader myReader = null;

                string sql = "select KARTOTEKA.indeks,STANMAG.standysp FROM kartoteka INNER JOIN stanmag using(ID_KARTOTEKA) WHERE stanmag.ID_MAGAZYN=10002;";
                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]);
                    if (standysp < 0)
                    {
                        standysp = 0;
                    }
                    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 ?? -1;
                }

                //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 = -1;
                    try
                    {
                        value = int.Parse(linia[1]);
                    }
                    catch (IndexOutOfRangeException)
                    {
                        index  = " - ZLE ZAPISANA LINIA";
                    }
                    catch (FormatException)
                    {
                        index  = " - PODANO ZLA WARTOSC";
                    }


                    if (zwr(index) == -1)
                    {
                        return new WynikPorownania { Indeks = index, Ilosc = (int)zwr(index) };
                    }
                    else
                    {
                        if (value < 0)
                        {
                            value = 0;
                        }
                        return new WynikPorownania { Indeks = index, Ilosc = (int)Math.Max(value, zwr(index)) };
                    }
                }).ToList();
            
                //DISPLAY ALL LISTATF CLASSES
                foreach (WynikPorownania WynikPorownania in listatf)
                {
                    Console.WriteLine(WynikPorownania);
                }

            return listatf;
            
        }
        public static void Main()
        {
            funkcjalista();
        }
    }
}

And here is the function where the error occures(the program underlines listadb after FirstOrDefault:

//RETURN STANDYSP FUNCTION
            double zwr(string myIndex)
            {
                var result = listadb.FirstOrDefault(listadb => listadb.index == myIndex)?.standysp;
                return result ?? -1;
            }

Thanks for help

CodePudding user response：

   var result = listadb.FirstOrDefault(listadb => listadb.index
                ^^^^^^^                ^^^^^^^

Don't call the parameter to the lambda the same as the list variable

        double zwr(string myIndex)
        {
            var result = listadb.FirstOrDefault(ldbitem => ldbitem.index == myIndex)?.standysp;
            return result ?? -1;
        }

(I changed listadb => listadb.index to ldbitem => ldbitem.index) - generally it's probably a more sensible naming practice anyway, for example if you had a list of cars, then the delegate parameter would be a car, because it's a single car being passed to the delegate, not multiple cars:

cars.ForEach(car => ...)