问题描述
使用以下代码，我尝试将在控制台中输入的用户追加到现有的csv文件中。我正在使用CSV帮助程序，并且已阅读文档。
首先，我从csv文件加载用户并将其存储在具有以下代码的列表中：
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Globalization;
using System.Linq;
using CsvHelper;
namespace GimpiesConsoleOOcsvListUI
{
public class UserList
{
public static List<User> LoadUsersFromCSV()
{
// using (var mem = new MemoryStream())
// using (var writer = new StreamWriter(mem))
using (var reader = new StreamReader("users.csv"))
using (var csvReader = new CsvReader(reader,CultureInfo.InvariantCulture))
{
// csvReader.Configuration.Delimiter = ";";
// csvReader.Configuration.IgnoreBlankLines = true;
csvReader.Configuration.HasHeaderRecord = true;
// csvReader.Configuration.PrepareHeaderForMatch = (string header,int index) => header.ToLower();
// csvReader.Configuration.MissingFieldFound = null;
csvReader.Read();
csvReader.ReadHeader();
// Store all content inside a new List as objetcs
var users = csvReader.GetRecords<User>().ToList();
return users;
// try
// {
// }
// catch (CsvHelper.HeaderValidationException exception)
// {
// Console.WriteLine(exception);
// }
}
}
}
}
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Globalization;
using System.Linq;
using CsvHelper;
namespace GimpiesConsoleOOcsvListUI
{
public class RegisterManager
{
public void Register(List<User> users)
{
// Get user input
Console.WriteLine("Enter username:");
string username = Console.ReadLine();
Console.WriteLine("Enter email:");
string email = Console.ReadLine();
Console.WriteLine("Enter password:");
string password = Console.ReadLine();
Console.WriteLine("Enter userrole (typ admin,purchase or sales):");
string userrole = Console.ReadLine();
// Create fresh instance to save input in memory
User user = new User(username,email,password,userrole);
// Adds the user to the excisting list
users.Add(user);
FileOperations fo = new FileOperations();
// Calling the method from FileOperations.cs to write the List here to a CSV file
fo.WriteUsersToCSV(users);
}
}
}
然后使用称为WriteUsersToCSV的方法将输入的用户写入现有的csv文件：
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Globalization;
using System.Linq;
using CsvHelper;
namespace GimpiesConsoleOOcsvListUI
{
// Handles CRUD within CSV files and able to save them
public class FileOperations
{
// Appends to CSV file from List
public void WriteUsersToCSV(List<User> users)
{
// Append to the file
using (var stream = File.Open("users.csv",FileMode.Append))
using (var writer = new StreamWriter(stream))
using (var csvWriter = new CsvWriter(writer,CultureInfo.InvariantCulture))
{
csvWriter.Configuration.HasHeaderRecord = false;
csvWriter.WriteRecords(users);
Console.WriteLine("New user added to users.csv");
}
}
// Writes to CSV file from List
public void WriteUsersToNewCSVFile(List<User> users)
{
using (var writer = new StreamWriter("users.csv"))
using (var csvWriter = new CsvWriter(writer,CultureInfo.InvariantCulture))
{
// csvWriter.Configuration.Delimiter = ";";
csvWriter.Configuration.HasHeaderRecord = true;
csvWriter.Configuration.AutoMap<User>();
csvWriter.WriteHeader<User>();
csvWriter.WriteRecords(users);
Console.WriteLine("New file users.csv created!");
}
}
// Reads from CSV file and displays content from it
public void ReadUsersFromCSV()
{
using (var reader = new StreamReader("users.csv"))
using (var csvReader = new CsvReader(reader,CultureInfo.InvariantCulture))
{
try
{
// csvReader.Configuration.Delimiter = ";";
// csvReader.Configuration.IgnoreBlankLines = true;
csvReader.Configuration.HasHeaderRecord = true;
// csvReader.Configuration.PrepareHeaderForMatch = (string header,int index) => header.ToLower();
// csvReader.Configuration.MissingFieldFound = null;
csvReader.Read();
csvReader.ReadHeader();
// Store all content inside a new List as objetcs
var records = csvReader.GetRecords<User>().ToList();
// Loop through the List and show them in Console (connect to values in the constructor User.cs record.username etc..)
foreach (var record in records)
{
Console.WriteLine($"{record.username } | {record.email} | {record.password} | {record.userrole}");
}
}
catch (CsvHelper.HeaderValidationException exception)
{
Console.WriteLine(exception);
}
}
}
// Writes to CSV file from List
public void SaveGimpiesToCSV(List<Gimpies> gimpies)
{
// using (var mem = new MemoryStream())
// using (var writer = new StreamWriter(mem))
using (var writer = new StreamWriter("gimpies.csv"))
using (var csvWriter = new CsvWriter(writer,CultureInfo.InvariantCulture))
{
csvWriter.Configuration.Delimiter = ";";
csvWriter.Configuration.HasHeaderRecord = true;
csvWriter.Configuration.AutoMap<Gimpies>();
csvWriter.WriteHeader<Gimpies>();
csvWriter.WriteRecords(gimpies);
writer.Flush();
// var result = Encoding.UTF8.GetString(mem.ToArray());
// Console.WriteLine(result);
}
}
}
}
但是当我写入现有的csv文件时，我又获得了前三个用户！查看结果：
username,userrole,Inkoop,inkoop@gimpies.nl,123,purchase
Verkoop,verkoop@gimpies.nl,sales
Beheer,beheer@gimpies.nl,admin
Inkoop,admin
Bas,bas@bas.nl,admin
在这里您看到我添加了用户Bas，但是又添加了Inkoop，Verkoop和Beheer。
确定这是我的Program.cs：
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Globalization;
using System.Linq;
using CsvHelper;
namespace GimpiesConsoleOOcsvListUI
{
class Program
{
static void Main(string[] args)
{
// List of default users
// List<User> users = UserList.DefaultUsers();
// Working on it... Try to read csv file first and try to read list from method in UserList.cs
// UserList ul = new UserList();
List<User> users = UserList.LoadUsersFromCSV();
// List<User> users =
// ul.LoadUsersFromCSV(users);
// Create login instance
LoginManager loginMgr = new LoginManager();
// Create stock instance
Stock stock = new Stock();
Start:
// Welcome message
Console.WriteLine("Welcome to the Gimpies Console Application! Choose 1 to login or 2 to exit this application:");
// Get input from user
string input = Console.ReadLine();
// Set to false to check if login fails or not
bool successfull = false;
while (!successfull)
{
if(input == "1")
{
Console.WriteLine("Enter your username:");
string username = Console.ReadLine();
Console.WriteLine("Enter your password:");
string password = Console.ReadLine();
foreach (User user in users)
{
if (username == user.username && password == user.password && user.userrole == "admin")
{
// Create Admin instance to be able to call methods in that class
Admin am = new Admin();
// Calling the method in Admin.cs to start Menu logic
am.AdminLoggedIn(users);
successfull = true;
break;
}
if (username == user.username && password == user.password && user.userrole == "purchase")
{
// Create Purchase instance to be able to call methods in that class
Purchase pc = new Purchase();
// Calling the method in Purchase.cs to start Menu logic
pc.PurchaseLoggedIn(users);
successfull = true;
break;
}
if (username == user.username && password == user.password && user.userrole == "sales")
{
// Create Sales instance to be able to call methods in that class
Sales sl = new Sales();
// Calling the method in Sales.cs to start Menu logic
sl.SalesLoggedIn(users);
successfull = true;
break;
}
}
if (!successfull)
{
Console.WriteLine("Your username or password is incorrect,try again !!!");
}
}
else if (input == "2")
{
Environment.Exit(-1);
}
else if (input == "3")
{
FileOperations fo = new FileOperations();
// Calling the method from FileOperations.cs to write the List here to a CSV file
fo.WriteUsersToCSV(users);
goto Start;
}
else if (input == "4")
{
FileOperations fo = new FileOperations();
// Calling the method from FileOperations.cs to write the List here to a CSV file
fo.ReadUsersFromCSV();
goto Start;
}
else
{
Console.WriteLine("Try again !!!");
break;
}
}
// // Loop over stored users within instances inside the list where users are added
// foreach (User user in users)
// {
// if(loginMgr.Login(user))
// {
// // Login successfull
// Console.WriteLine("Login user " + user.UserName);
// }
// else
// {
// // Not successfull
// }
// }
}
}
}
我的GitLab存储库：https://gitlab.com/marianydesign/gimpiesconsoleoocsvlist
解决方法
我为您提供了两种选择。确保仅实现两个选项之一。
选项＃1 （您的代码正在尝试实现的选项），您可以将新记录追加到文件数据中。此选项将要求您跟踪文件中已有的内容，以便排除写入文件中已有的记录。
选项＃2 ，您每次都可以使用完整的用户列表覆盖文件。每次都不必追加完整的文件写入。
实施选项1：
此选项仅需更改您的(a >=> b) >=> c条件内。更新条件，以便将要写入的列表与文件中已有的内容进行比较，并排除写入文件中已有的任何else if (input == "3") ...
UsersOR
实施方案2：
此选项需要更改您的else if (input == "3")
{
FileOperations fo = new FileOperations();
// get existing users from file
List<User> userInFile = UserList.LoadUsersFromCSV();
// remove existing users from update list to create final list for writing
List<User> finalList = users.Where(u => !userInFile.Any(uf => uf.email.Equals(u.email,StringComparison.InvariantCultureIgnoreCase))).ToList();
fo.WriteUsersToCSV(users);
goto Start;
}
方法。
WriteUsersToCSV