Operator Overloading causes a stack overflow

Question

I started out programming with C# a few days ago.

Now an confusing error arised when playing around with operator overloading.

The following code produces a StackOverflowException when running:

using System;

namespace OperatorOverloading
{
    public class Operators
    {
        // Properties
        public string text
        {
            get
            {
                return text;
            }

            set
            {
                if(value != null)
                    text = value;
                else
                    text = "";
            }
        }

        // Constructors
        public Operators() : this("")
        {
        }

        public Operators(string text)
        {
            // Use "set" property.
            this.text = text;
        }

        // Methods
        public override string ToString()
        {
            return text;
        }

        // Operator Overloading
        public static string operator +(Operators lhs, Operators rhs)
        {
            // Uses properties of the passed arguments.
            return lhs.text + rhs.text;
        }

        public static void Main(string[] args)
        {
            Operators o1 = new Operators();
            Operators o2 = new Operators("a");
            Operators o3 = new Operators("b");

            Console.WriteLine("o1: " + o1);
            Console.WriteLine("o2: " + o2);
            Console.WriteLine("o3: " + o3);

            Console.WriteLine();

            Console.WriteLine("o1 + o2: " + (o1 + o2));
            Console.WriteLine("o2 + o3: " + (o2 + o3));
        }
    }
}

I tried to write an own example after reading the chapter about operater overloading from the book "Microsoft Visual C# 2008" from Dirk Louis and Shinja Strasser.

Maybe someone has a clue what's going wrong.

Thanks.

your Main is inside the Operators class, is that something you wanted to do on purpose? — Kris Ivanov
– Kris Ivanov, Commented Feb 27, 2011 at 17:28
Just curious... why the accepted answer change from mine to curious geek's? The general rules are to mark the first answer that provided a working solution as accepted. — Cᴏʀʏ
– Cᴏʀʏ, Commented Feb 27, 2011 at 18:01

Cᴏʀʏ · Accepted Answer · 2011-02-27 17:43:25Z

10

Well, for one, the operator overloading isn't breaking your code. You get a StackOverflowException because your text property's getter is trying to return itself.

You should use a backing field for your property:

private string _text;

public string Text
{
    get { return _text; }
    set
    {
        if (value != null)
            _text = value;
        else
            _text = string.Empty;
    }
}

What .NET does under the covers is convert your property into an accessor and a mutator -- two separate methods. In your original example, your code would be doing the following:

private string text;

public string get_text()
{
    return get_text(); // <-- StackOverflowException
}

public void set_text(string value)
{
    this.text = value;
}

Whereas the corrected version uses the backing field properly:

private string text;

public string get_text()
{
    return this.text; // Happy :)
}

public void set_text(string value)
{
    this.text = value;
}

edited Feb 27, 2011 at 17:43

answered Feb 27, 2011 at 17:25

Cᴏʀʏ

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2 Comments

Mike Caron Over a year ago

I see plenty of operator overloading. However, you are correct in your answer.

Cᴏʀʏ Over a year ago

@Mike - Yes, I didn't scroll down far enough. Whoopsy!

this. __curious_geek · Accepted Answer · 2011-02-27 17:46:35Z

2

The get code-block in your class has the problem and that is what is causing the StackOverFlow exception.

    public string text
    {
        get
        {
            return text;
        }
    }

Here when you say return text; it will go and call the get block of the property text itself which is causing the stack-overflow. wrap your property text around a private _txt string field and it should work properly.

You can make it something like this..

private string _txt;
public string text
{
    get
    {
        return _txt;
    }

    set
    {
        _txt = string.IsNullOrEmpty(value) ? string.Empty : value;
    }
}

edited Feb 27, 2011 at 17:46

answered Feb 27, 2011 at 17:28

this. __curious_geek

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Comments

Matteo TeoMan Mangano · Accepted Answer · 2011-02-27 17:30:07Z

1

The problem is that the text proprty returns itself You should have a protected or private variab le to store the resut:

// Properties
    private string _text
    public string text
    {
        get
        {
            return _text;
        }

        set
        {
            if(value != null)
                _text = value;
            else
                _text = "";
        }
    }

answered Feb 27, 2011 at 17:30

Matteo TeoMan Mangano

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