C#•3mo ago

Need help selecting objects in a list

This code is simply a testing file so I can figure out how to make this work. In this file I created the class Hero with three int values id, lvl, hp. A friend explained how to set this up so that I can create objects via this class. I'm not sure why the int's need to be declared three times or what the 'this' statement does or why it is needed, an explanation on this would be nice but not necessary at the moment. What I'd like to do in this file is allow the user to pick a Hero. line 29 creates the Hero list, line 30 and 31 allow user input. 33 and 34 are objects, the test Hero's named dee and goo. Lines 37 and 47 are my various attempts at getting trying to get the listing to appear and for me and to be able to select something in the list but unfortunately the foreach and for don't work, I tried LinqQuery but I'm not even sure how that works. On lines 57 to 61 you can see testing on object manipulation but unfortunately it's hard coded to the first Hero 'dee'. I don't know what I would type in instead to allow for a more generic object value changes depending on which Hero was selected. Please I am a beginner at C# coding and I do not understand all the terms so please if possible answer in layman's terms so I can understand better. Thank you.

53 Replies

Angius•3mo ago

an explanation on this would be nice but not necessary at the moment

Go through the $helloworld tutorials, they will explain things like variables, classes, objects, instances, and so on.

What I'd like to do in this file is allow the user to pick a Hero. line 29 creates the Hero list

No heroes are ever added to the list, the list is and will be empty

MODiX•3mo ago

Interactive course https://learn.microsoft.com/en-us/training/paths/get-started-c-sharp-part-1/ Videos https://dotnet.microsoft.com/learn/videos

Angius•3mo ago

You have variable dee with a hero, variable doo with a hero, but none of them are in the list Trying to foreach through an empty list just does nothing

ShrowOP•3mo ago

Oh now how do I add objects to the the list then? The same friend told me that a the code on the learn Microsoft is poorly written and was going to teach me bad habits. Something about “if this code was presented to a professor, they would fail it.” At my level I cant tell what’s wrong with it. Il go back to it. It’s better then making no progress. Thank you for help

Angius•3mo ago

In my experience, it's often the professors who know fuck all about programming Initializing a new list with elements is simple, there are a few ways: The long way:

var list = new List<int>();
list.Add(1);
list.Add(71);
list.Add(881);

var list = new List<int>();
list.Add(1);
list.Add(71);
list.Add(881);

List initializer:

var list = new List<int>(){ 1, 71, 881 };

var list = new List<int>(){ 1, 71, 881 };

Collection expression:

List<int> list = [1, 71, 881];

List<int> list = [1, 71, 881];

In your case, it will be a list of Heros, so for example

List<Hero> heroes = [
    new Hero("Bob", 1, 2, 3),
    new Hero("Matilda", 6, 7, 8),
    // etc...
];

List<Hero> heroes = [
    new Hero("Bob", 1, 2, 3),
    new Hero("Matilda", 6, 7, 8),
    // etc...
];

ShrowOP•3mo ago

Noted il try this! Thank you

TizzyT•3mo ago

1) this keywork is to refer to the current instance of what ever object the class made. So if you have a Hero class and later you make a Hero object. The this keyword is a way for that object to reference itself. 2) maybe a record (instead of class maybe simpler in your case). 3) To list all the Heros loop through and print the Hero.

public record Hero(string Name, int Id, int Lvl, int Hp);

List<Hero> heros = new();
heros.Add(new("dee", 1, 3, 30));
heros.Add(new("goo", 1, 4, 40));

// List Heros
for(int i = 0; i < heros.Count; i++);
  Console.WriteLine($"{i} : {Heros[i]}");

// Get user input
Hero? userSelection = null;
while (userSelection is null)
{
  Console.WriteLine("Select a Hero");
  string userInput = Console.ReadLine();
  if (int.TryParse(userInput, out int index) && index > -1 && index < heros.Count)
  {
    userSelection = heros[index];
  }
  else
  {
    Console.WriteLine("Invalid input, Try Again");
  }
}

// Print the selected hero
Console.WriteLine($"You Selected the Hero: {userSelection.Name}");

public record Hero(string Name, int Id, int Lvl, int Hp);

List<Hero> heros = new();
heros.Add(new("dee", 1, 3, 30));
heros.Add(new("goo", 1, 4, 40));

// List Heros
for(int i = 0; i < heros.Count; i++);
  Console.WriteLine($"{i} : {Heros[i]}");

// Get user input
Hero? userSelection = null;
while (userSelection is null)
{
  Console.WriteLine("Select a Hero");
  string userInput = Console.ReadLine();
  if (int.TryParse(userInput, out int index) && index > -1 && index < heros.Count)
  {
    userSelection = heros[index];
  }
  else
  {
    Console.WriteLine("Invalid input, Try Again");
  }
}

// Print the selected hero
Console.WriteLine($"You Selected the Hero: {userSelection.Name}");

Hope i didnt make any mistake

ShrowOP•3mo ago

I'm getting the error "CS8936 Feature 'collection expressions' is not available in C# 10.0. Please use language version 12.0 or greater." I didn't realize my file was not updated to the most recent version, real quick could you tell me how to do that?

Angius•3mo ago

Ah, seems your project uses an old version of .NET, .NET Framework probably $newproject

MODiX•3mo ago

When creating a new project, prefer using .NET over .NET Framework, unless you have a very specific reason to be using .NET Framework. .NET Framework is now legacy code and only get security fix updates, it no longer gets new features and is not recommended. https://cdn.discordapp.com/attachments/569261465463160900/899381236617855016/unknown.png

Angius•3mo ago

For reference

TizzyT•3mo ago

double click on the project file and add

<LanguageVersion>latest</LanguageVersion>

<LanguageVersion>latest</LanguageVersion>

ShrowOP•3mo ago

Oh I will test this out for sure thank you

Angius•3mo ago

The easiest way would be to make a new project without the (.NET Framework) suffix and just copy your code over, IMO Changing the language version will hardly be enough You would need to change the framework version as well, best to keep them in sync .NET 8 -> C# 12 Ah, wait, C# 10 is .NET 6, right? In that case, yeah, updating the language version and framework version will be enough

TizzyT•3mo ago

i dont remember either lol

Angius•3mo ago

Right-click the project, open properties, you'll be able to change it there

TizzyT•3mo ago

I just know that 10 is far back enough that if you have .net installed you most likely are upto date enough

ShrowOP•3mo ago

Hmm I only have .Net 8.0 as the newest option. I guess my visual studio is out of date

Angius•3mo ago

That's the newest one

TizzyT•3mo ago

.Net8 is definitely upto date lol um id say just change the language version and you should be good, follow what @ZZZZZZZZZZZZZZZZZZZZZZZZZ said Tho I have never changed it from there so idk

ShrowOP•3mo ago

well it was out of date just from 17.10.4 to 17.11.4 after update i'l fix my file

TizzyT•3mo ago

thats the visual studio version, but I guess you can update that too if you want.

TizzyT•3mo ago

I tend to just double click on the project file (the green one):

ShrowOP•3mo ago

Okay good to know what the project file was because I wasn't 100% sure

TizzyT•3mo ago

then just add the <LanguageVersion> like so:

Angius•3mo ago

Change that netstandard2.0 to net8.0

TizzyT•3mo ago

source generators

Angius•3mo ago

Ah, carry on then

TizzyT•3mo ago

🙂

ShrowOP•3mo ago

okay it's working now to actually print the list @TizzyT What's a record keyword? Is that similar to class?

Angius•3mo ago

It's a spicy class, yes Compiles to a class, but has a bunch of added functionality And is immutable by default

TizzyT•3mo ago

oh yeah, i probably shouldve mentioned that

ShrowOP•3mo ago

@TizzyT I am using it right? I'm seeing lots of red

TizzyT•3mo ago

move the public record outside of the method (before Main) indent the line:

Console.WriteLine($"{i} : {Heros[i]}");

Console.WriteLine($"{i} : {Heros[i]}");

same line, change the H to h You can change

string userInput = Console.ReadLine();

string userInput = Console.ReadLine();

string? userInput = Console.ReadLine();

string? userInput = Console.ReadLine();

string userInput = Console.ReadLine()!;

string userInput = Console.ReadLine()!;

if you really want to get rid of the squigglies once this works you can then move onto make Hero a class 😛

ShrowOP•3mo ago

IT's working! Thank you, Tizzy What do you mean? It's already a class with the 'this' statements right?

TizzyT•3mo ago

the this statement only allows an object to reference itself. It doesnt make something a class right now you have a Heros as records. You can modify this to have things like lvl, hp, etc be changed but as it is now you cannot change it without creating a whole new instance with the "with" keyword so like I mentioned you can modify what you have now to

public record Hero
{
  // implementation
}

public record Hero
{
  // implementation
}

or you can just go back to a class either of which will look pretty similar

ShrowOP•3mo ago

So I can't do Doo.hp + 5; without creating a whole new instance?

Angius•3mo ago

I'd stick with a class Let's keep it simple With records, not exactly, no With classes, yes

ShrowOP•3mo ago

Why make it a record then?

Angius•3mo ago

Takes less code That's mostly the reason And such immutability is sometimes desired Not in this case, though

ShrowOP•3mo ago

oh okay

TizzyT•3mo ago

public class Hero
{
  public string Name { get; set; }
  public int Id { get; set; }
  public int Lvl { get; set; }
  public int Hp { get; set; }

  public Hero(string name, int id, int lvl, int hp)
  {
    Name = name;
    Id = id;
    Lvl = lvl;
    Hp = hp;
  }
}

public class Hero
{
  public string Name { get; set; }
  public int Id { get; set; }
  public int Lvl { get; set; }
  public int Hp { get; set; }

  public Hero(string name, int id, int lvl, int hp)
  {
    Name = name;
    Id = id;
    Lvl = lvl;
    Hp = hp;
  }
}

ShrowOP•3mo ago

So this is the ideal way to do it? I will test

Angius•3mo ago

A class? Yes

TizzyT•3mo ago

I mean you can experiment and learn the advantages and disadvantages first hand 🙂

ShrowOP•3mo ago

And it works, Thank you!

TizzyT•3mo ago

It doesnt have to take more code, you can turn it into a single line too

public class Hero(string Name, int Id, int Lvl, int Hp);

public class Hero(string Name, int Id, int Lvl, int Hp);

The reason to use records is because it has some things implemented behind the scenes which are nice in certain scenarios like ToString is already implemented for you etc like mentioned earlier it is basically just a fancy class and I guess a

record struct

record struct

is a fancy struct

Angius•3mo ago

This won't work

ShrowOP•3mo ago

oh thanks for tip however I'd prefer to keep it longer for now.

Angius•3mo ago

Primary constructor parameters in classes are just parameters. Only records compile them into properties.

ShrowOP•3mo ago

good to know, I don't like declaring values in the constructor anyway.

TizzyT•3mo ago

oops, apologies: this then:

class Hero(string name, int id, int lvl, int hp)
{
    public string Name { get; set; } = name;
    public int Id { get; set; } = id;
    public int Lvl { get; set; } = lvl;
    public int Hp { get; set; } = hp;
}

class Hero(string name, int id, int lvl, int hp)
{
    public string Name { get; set; } = name;
    public int Id { get; set; } = id;
    public int Lvl { get; set; } = lvl;
    public int Hp { get; set; } = hp;
}

Angius•3mo ago

This would work, yes

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Need help selecting objects in a list