为什么我的现有客户数量不断增加？

Question

我的任务是修复一些代码。每次程序运行时，它都会变得越来越慢。通过使用一些断点和分析，我认为我缩小了它背后的原因，但是我不确定如何解决它。

这个函数使用了大量的 cpu，我将它缩小到我的现有客户端变量，该变量无限期地添加 https://gyazo.com/67e44844a279a10e1b11165b941b1cf6

public void AddNewClientData()
{
  Logger logger = LogManager.GetCurrentClassLogger();

  try {
    string[] fileLines = File.ReadAllLines("ClientList.csv");
    foreach(string line in fileLines)
    {
      string[] lineParts = line.Split(',');
      Client client = new Client()
      {
        ClientName = lineParts[0],
          ClientPhone = lineParts[1],
          EntryTime = DateTime.Parse(lineParts[2]),
          ExitTime = DateTime.Parse(lineParts[3])
      };

      bool clientExists = false;

      // Check that the user does not already exist
      string sqlGet = "Select * FROM ClientInOut";
      using(var connection = Helpers.GetConnection())
      {

        connection.Open();
        List < Client > existingClients = connection.Query<Client>(sqlGet).ToList();

        for (int i = 0; i < fileLines.Length; i++)
        {
          foreach(Client existingCustomer in existingClients)
          {

            if (existingCustomer == client) {
              clientExists = true;

            }
          }

        }

      }
    // add the new client 
    if (clientExists == false) {
      string sql =
        "INSERT INTO ClientInOut (ClientName, ClientPhone, EntryTime, ExitTime) Values (@ClientName, @ClientPhone, @EntryTime, @ExitTime);";
      using(var connection = Helpers.GetConnection())
      {
        connection.Open();
        var affectedRows = connection.Execute(sql, client);
      }
    }

  }
}

Answer 1

== 运算符将比较对象引用，因此 existingCustomer == client 将返回 false（因为它们是不同的对象，因此它们不共享相同的引用）并且您最终会插入您的客户端。

我建议覆盖 Equals 并使用它而不是 ==。

看下面的sn-p（只有两个属性可以避免噪音）：

using System.IO;
using System;

public class Client
{
    public string Name { get;set; }
    public string Phone { get;set; }
    
    public override bool Equals(object other)
    {
        if(other is Client)
        {
            var c2 = (Client)other;
            // Compare the properties instead of objects references
            return c2.Name == this.Name && c2.Phone == this.Phone;
        }
        return false;
    }
}

class Program
{
    static void Main()
    {
        Client c1 = new Client
        {
            Name = "Test",
            Phone = "0055512345"
        };
        Client c2 = new Client
        {
            Name = "Test",
            Phone = "0055512345"
        };
        
        Console.WriteLine(c1 == c2);      // returns false
        Console.WriteLine(c1.Equals(c2)); // returns true
    }
}

---

注意这是极简代码，如果你选择这样，你可以改进很多：

• 添加null签入Equals代码
• 如果您使用足够新的 c# 版本进行编码，请使用类型模式匹配
• 也覆盖 GetHashCode 以消除警告
• 等