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.

Answer 1

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;
}