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What is an indexer, and how does it let a custom class support square-bracket syntax like an array? How do you overload the '+' operator to support adding two custom objects together? How do you overload comparison operators like < and >, and what consistency rule must they maintain relative to Equals()? How do you define a custom implicit or explicit conversion operator between your type and another type? How would you implement a multi-dimensional indexer, like a Matrix class supporting matrix[row, col] syntax? How do you overload the true/false operators to make a custom type usable directly in an 'if' statement or as a boolean condition? How would you implement a fluent, chainable custom '+' operator overload for building an immutable Vector3 math library, and what performance consideration applies for structs? How do you implement the 'checked' operator overload variant (introduced in C# 11) to provide overflow-checking behavior for a custom numeric type? How would you use an indexer together with a custom enumerator (implementing IEnumerable) to build a fully iterable, indexable custom collection class?
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C# › Indexers & Operator Overloading

Which operators can be overloaded in C#, and which ones (like && and ||) generally CANNOT be overloaded directly?

Intermediate

Answer

You can overload most unary and binary operators (+, -, *, /, ==, !=, <, >, etc.), true/false, and implicit/explicit conversion operators — but && and || specifically CANNOT be overloaded directly (they're derived automatically from overloading & and | plus true/false operators), and assignment operators like = can never be overloaded at all.
public static Vector operator +(Vector a, Vector b) => new(a.X + b.X, a.Y + b.Y); // OK
public static Vector operator *(Vector v, double scalar) => new(v.X * scalar, v.Y * scalar); // OK
// public static Vector operator &&(Vector a, Vector b) { } // NOT directly overloadable
Real-world example Deciding which operators genuinely make semantic sense to overload for a custom Vector, Money, or Complex number type.

Common follow-ups: How would you make a custom type work correctly with '&&' indirectly, given it can't be overloaded directly?

OOP
All 10 Indexers & Operator Overloading questions