C# using get set. Why is this failing?

Brian_TheLion

I can't see the reason why this does not work. There is no clear indication what the error is.

public int CurrentHitPoints { get; set; }
public int MaximumHitPoints { get; set; }
public int Gold
{
get
{
return Gold;
}

        set
        {
            if (value == 20)
           {
              value += 5;
              Gold = value;
           }
        }
    }
    public int ExperiencePoints { get; set; }
    public int Level { get; set; }

Brian

Member 13566383

What do you mean by "is failing"?

Brian_TheLion

I get this popup box An unhandled exception of type 'System.StackOverflowException' occurred in Engine.dll Engine is a container for player.cs Brian

Member 13566383

You are calling your get- and set-properties for "Gold" recursively.

Brian_TheLion

This is the code that player.cs is called from. I added a TEST button. lblGold.text is a label on the form.

using Engine;

namespace SuperAdventure
{
public partial class SuperAdventure : Form
{
private Player _player;

    public SuperAdventure()
    {
        InitializeComponent();

        Location location = new Location(1, "Home", "This is your house.");


        \_player = new Player(10, 10, 20, 0, 1);
        
        Update();

    }

    private void btnTest\_Click(object sender, EventArgs e)
    {
        \_player.Gold = 30;
        //  lblGold.Text = \_player.Gold.ToString();
        Update();
    }
          public void  Update()
      {
        lblHitPoints.Text = \_player.CurrentHitPoints.ToString();
        lblGold.Text = \_player.Gold.ToString();
        lblExperience.Text = \_player.ExperiencePoints.ToString();
        lblLevel.Text = \_player.Level.ToString();
    }
}

}

lmoelleb

Your highest priority should be to learn to use the debugger. It might sound advanced... but it isn't. You will be able to spot the course of errors like this in seconds - even without a heap of experience. Sure some errors will still be tricky... but if they are tricky with a debugger, they are pretty much impossible to solve without. All you have to do is set a break point in the code you see a problem with (F9 in Visual Studio default key binding). Start the program with the debugger attached (F5) and reproduce the problem. Now you can step through the program line by line (F10/F11)- and you can see the values of all variables and fields at each line in the program. Spotting the setter calling itself is trivial this way. As a beginner you might still want to ask help on how to solve a problem once you identified it - but at least you can ask a much more precise question when you know what the error is - and get help a lot easier. So please - take the time to learn the debugger. The half hour will come back with interest of a few million percent.

OriginalGriff

Look at your code.

public int Gold
{
get
{
return Gold;
}
...
}

So now lets use it:

int g = myClassInstance.Gold;

It enters the Gold getter, which returns the value of ... the Gold getter. Which returns the value of ... the Gold getter. Which returns the value of ... the Gold getter. ... until the stack blows and your app crashes. The same happens when you try to use the setter: it infinitely recurses trying to set itself! Create a private backing field:

private int _Gold = 0;
public int Gold
{
get
{
return _Gold;
}

set
    {
    if (value == 20)
        {
        value += 5;
        \_Gold = value;
        }
    }
}

And it'll all work.

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

Brian_TheLion

I normally have an error message popup that tells me e exactly what is wrong (in most cases it's a spelling mistake) but this time this did not happen. I have stepped through programs to see how they work. I could try doing that but I suspect all that would happen is the same message would pop up which does not tell me exactly what is wrong. However a popup box with same message is better than nothing. I may need to research this message on the internet Brian

Brian_TheLion

Tbanks Griff. It looks like I've created a continuous loop. I'll try what you have suggested. I noticed that you used _Gold instead of Gold. Brian

Pete OHanlon

_Gold is a member variable. Gold is the property that exposes the variable. Basically, if you attempt to get a property and return the property name instead of a variable, you're going to repeatedly call the same getter. This is what causes the StackOverflowException.

This space for rent

OriginalGriff

Not a continuous loop, but an "unbounded recursion" - similar thing, but the later will blow the stack at some point. Just to add to what Pete says, the naming conventions say that a backing field should have the same name as the property it is associated with, but prefixed with underscore:

private int _MyProperty;
public int MyProperty
{
get { return _MyProperty; }
set { _MyProperty = value; }
}

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

lmoelleb

Rule number 2 when troubleshooting (rule number one is "use the debugger") is not to assume anything. Assuming your debugger won't show you what is wrong is not the right approach. What would happen if you had spend 10 seconds setting a breakpoint in the getter and setter and then kept pressing F11: You would see your code repeatedly call itself, while the callstack keeps growing one line each time it calls itself.

BillWoodruff

I twitch when I see a private backing field that has an uppercase letter following an initial underscore : :wtf: I'm sorry. However, when I consider this example is still current in the MS docs [^]:

public enum Color {...}
public class Control {
public Color Color { get {...} set {...} }
}

I throw up. Remember the daze when common practice was to use: _mSomeName ?

«Where is the Life we have lost in living? Where is the wisdom we have lost in knowledge? Where is the knowledge we have lost in information?» T. S. Elliot

Lost User

[Using Properties - C# Programming Guide | Microsoft Docs](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/using-properties)

The Master said, 'Am I indeed possessed of knowledge? I am not knowing. But if a mean person, who appears quite empty-like, ask anything of me, I set it forth from one end to the other, and exhaust it.' ― Confucian Analects

kalberts

Seriously: Are there really people out there NOT using a debugger when developing code? To me that is like climbing Mt.Everest blindfolded, all on your own. There may be extreme exceptions where no traditional debugger is available or can't be used, e.g. in a certain class of embedded systems where the code is in flash memory and cannot be modified on a byte or word basis, so you can't poke debug interrupts. Or the processor is so primitive that it doesn't provide interrupts, or doesn't give sufficient external access to the address bus to run a probe on the outside. But those are very special cases. And I have never seen a system where you cannot do "printf style" debugging by setting output signals - even 8-bit embedded processors offer that (otherwise, how would they control what they are supposed to control?) Those special cases are lightyears away from desktop development in C#. If you run a company, you most certainly can affort the investment in, say, Visual Studio. For hobby programming, there is a free version providing so near-100% functionality that you probably won't notice the difference. (There are some differences, but they are rarely relevant for hobby programming.) Even printf debugging can work well in some cases (sometimes it is usesful as a companion to the interactive debugger, e.g. to traverse data structures and print selected values if this requires more processing than a simple watch expression). But "debugging by cranial massage", as one University lecturer phrased it. is not sufficient.

Member 13566383

Error messages which tell you about spelling mistakes or other syntax errors are generated at compile time of your program. No executable is produced and therefore your program doesn't run. A stack overflow condition can only occur when your program has been compiled and started running. The debugger is the tool to be used for analyzing run time errors. You should learn to understand the difference between these to error types.

Lost User

Sadly yes. The number of QA posts that show the user has made no attempt to do even basic debugging, continues to amaze (and worry) me.

Dave Kreskowiak

There is no message you could possibly get that will tell you "exactly what is wrong" when the logic in your app is what is wrong. The error message you get can even be misleading. Using the debugger to step through the code is THE most powerful tool you can use to find problems, not error messages. Error messages are a symptom of the problem, not the solution to it.

Asking questions is a skill CodeProject Forum Guidelines Google: C# How to debug code Seriously, go read these articles.
Dave Kreskowiak

Brian_TheLion

Hi Griff. Your change worked when there was a test for the value of 20 but when I changed the test value to 30 then 0 was displayed on the form for the amount of gold, then when I clicked on the Test button the gold value changed to 35. What I'm aiming at on this test is for 20 to first to appear on the form for the Gold value after the program is run, then when I press the Test button the gold value should change to 30 and in the test have 5 added to the 30 giving a gold value of 35. Here is my code On the main program I have SuperAdventure.cs

public partial class SuperAdventure : Form { private Player _player; public SuperAdventure() { InitializeComponent(); Location location = new Location(1, "Home", "This is your house."); _player = new Player(10, 10, 20, 0, 1); Update(); } // TEST Button on Form private void btnTest_Click(object sender, EventArgs e) { _player.Gold = 30; Update(); } public void Update() { lblHitPoints.Text = _player.CurrentHitPoints.ToString(); lblGold.Text = _player.Gold.ToString(); lblExperience.Text = _player.ExperiencePoints.ToString(); lblLevel.Text = _player.Level.ToString(); } } } Player.cs code namespace Engine { public class Player { // This is needed for _player = new Player(10, 10, 20, 0, 1,); public int CurrentHitPoints { get; set; } public int MaximumHitPoints { get; set; } private int _Gold = 0; public int Gold { get { return _Gold; } set { if (value == 30) { value += 5; _Gold = value; } } } public int ExperiencePoints { get; set; } public int Level { get; set; } //In order to use lists – we need one variable or property to hold a collection of objects that are the same class public List Inventory { get; set; } public List Quests { get; set; } // This is needed for lblHitPoints.Text = _player.CurrentHitPoints.ToString() etc; public Player(int currentHitPoints, int maximumHitPoints, int gold,

Brian_TheLion

But isn't the program debugging when it compiles. I normally get an error message if the compiler can't compile the code. Maybe your talking about some other debugging. Brian