Is it always necessary to avoid overloading the Equals method or the == operator in classes?

It is not always necessary to avoid overloading the Equals method or the == operator in classes. On the contrary, in C# it is often recommended to override Equals (and GetHashCode) for correct comparison of objects by value rather than by reference.

However, it is important:

• To correctly implement Equals and GetHashCode together to maintain the hashing contract.
• If the == operator is overloaded, then the != operator should also be overloaded.
• To avoid overloading if reference comparison is sufficient and there is no need for content comparison.

Example of overriding Equals and the == operator:

public class Point
{
    public int X { get; set; }
    public int Y { get; set; }

    public override bool Equals(object obj)
    {
        if (obj is Point other)
            return X == other.X && Y == other.Y;
        return false;
    }

    public override int GetHashCode() => HashCode.Combine(X, Y);

    public static bool operator ==(Point left, Point right) => Equals(left, right);
    public static bool operator !=(Point left, Point right) => !Equals(left, right);
}

Thus, overloading is useful and often necessary, but requires careful implementation.