Operator Overloading in C#

Operator overloading enables custom behavior for operators when working with user-defined types. Key aspects include:

• Only applicable to classes and structs
• Implemented through static methods named operator followed by the symbol (e.g., operator +)
• Must be members of the class/struct they operate on

Syntax Patterns

Unary operators (single operand):

public static CustomType operator -(CustomType operand)
{
    return new CustomType(-operand.Value);
}

Binary operators (two operands, at least one must be the containing type):

public static CustomType operator -(CustomType left, CustomType right)
{
    return new CustomType(left.Value - right.Value);
}

Practical Example

class BoundedNumber
{
    private const int Max = 100;
    private const int Min = 0;
    
    private int _value;
    public int Value
    {
        get => _value;
        set => _value = Math.Clamp(value, Min, Max);
    }

    public BoundedNumber(int value = 0) => Value = value;

    // Unary negation
    public static BoundedNumber operator -(BoundedNumber num)
    {
        return new BoundedNumber(-num.Value);
    }

    // Subtraction
    public static BoundedNumber operator -(BoundedNumber a, BoundedNumber b)
    {
        return new BoundedNumber(a.Value - b.Value);
    }

    // Double addition
    public static BoundedNumber operator +(BoundedNumber num, double add)
    {
        return new BoundedNumber(num.Value + (int)add);
    }
}

Operator Overloading Constraints

Restrictions:

• Cannot create new operators
• Cannot modify operattor syntax
• Cannot alter behavior for built-in types
• Cannot change operator precedence

Special Considerations for Increment/Decrement

For reference types:

• Prefix (++x) modifies and returns the original object
• Postfix (x++) modifies the original but returns a reference to the modified object

class Counter
{
    public int Count { get; set; }
    
    public static Counter operator ++(Counter c)
    {
        c.Count++;
        return c;
    }
}

var counter = new Counter { Count = 1 };
Console.WriteLine(counter++.Count); // Outputs 2 (modified value)