创建Computer对象存入列表无输出及对象列表未存条目的问题

Hey there, let's work through your two problems and get things working properly!

Issue 1: Object List Won’t Store Entries or Display Content #

The most common reason for this is not initializing your list correctly. If you only declare a List<Computer> variable without creating a new instance of the list, adding items will either fail silently or throw a null reference error.

Fix Example: #

// Initialize the list properly before adding items
List<Computer> computerInventory = new List<Computer>();

// Add a fully constructed Computer object to the list
computerInventory.Add(new Computer("Dell", "HQ Server Room", "SRV-01", "PC-123", "2024-05-20 14:30"));

Also double-check that you’re not trying to add a null Computer object to the list—every entry needs to be a fully instantiated instance using your constructor.

Issue 2: No Output When Viewing Computer Object Data #

Looking at your partial class code, two key issues are causing this:

1. Your class properties (companyName, locationName, etc.) are private by default, so you can’t access their values outside the class.
2. You haven’t overridden the default ToString() method, so printing the object will just show the type name instead of meaningful data.

Fixed Computer Class Code: #

class Computer 
{
    // Make properties publicly accessible (using get-only properties for immutability)
    public string CompanyName { get; }
    public string LocationName { get; }
    public string ServerName { get; }
    public string DeviceName { get; }
    public string LastOnline { get; }

    // Complete constructor to set all properties
    public Computer(string companyName, string locationName, string serverName, string deviceName, string lastOnline) 
    {
        CompanyName = companyName;
        LocationName = locationName;
        ServerName = serverName;
        DeviceName = deviceName;
        LastOnline = lastOnline;
    }

    // Override ToString() to display human-readable data when printing the object
    public override string ToString()
    {
        return $"Device: {DeviceName} | Company: {CompanyName} | Location: {LocationName} | Last Online: {LastOnline}";
    }
}

How to View the Data Now: #

• Print a single Computer object:

  Computer myPC = new Computer("HP", "Remote Office", "SRV-02", "PC-456", "2024-05-20 15:15");
  Console.WriteLine(myPC); // Uses our custom ToString() output
  

• Loop through your list to display all entries:

  foreach (var computer in computerInventory)
  {
      Console.WriteLine(computer);
  }
  

Quick Recap #

• Always initialize your list with new List<Computer>() before adding items.
• Make class properties accessible (public or with getters) to read their values outside the class.
• Override ToString() to get useful output when printing objects.

内容的提问来源于stack exchange，提问作者Ollie Beumkes