Overloading assignment operator in C#

Question

I know the = operator can't be overloaded, but there must be a way to do what I want here:

I'm just creating classes to represent quantitative units, since I'm doing a bit of physics. Apparently I can't just inherit from a primitive, but I want my classes to behave exactly like primitives -- I just want them typed differently.

So I'd be able to go,

Velocity ms = 0;
ms = 17.4;
ms += 9.8;

etc.

I'm not sure how to do this. I figured I'd just write some classes like so:

class Power
{
    private Double Value { get; set; }

    //operator overloads for +, -, /, *, =, etc
}

But apparently I can't overload the assignment operator. Is there any way I can get this behavior?

Answer 1

It sounds like you should be using a struct rather than a class... and then creating an implicit conversion operator, as well as various operators for addition etc.

Here's some sample code:

public struct Velocity
{
    private readonly double value;

    public Velocity(double value)
    {
        this.value = value;
    }

    public static implicit operator Velocity(double value)
    {
        return new Velocity(value);
    }

    public static Velocity operator +(Velocity first, Velocity second)
    {
        return new Velocity(first.value + second.value);
    }

    public static Velocity operator -(Velocity first, Velocity second)
    {
        return new Velocity(first.value - second.value);
    }

    // TODO: Overload == and !=, implement IEquatable<T>, override
    // Equals(object), GetHashCode and ToStrin
}

class Test
{
    static void Main()
    {
        Velocity ms = 0;
        ms = 17.4;
        // The statement below will perform a conversion of 9.8 to Velocity,
        // then call +(Velocity, Velocity)
        ms += 9.8;
    }
}

(As a side-note... I don't see how this really represents a velocity, as surely that needs a direction as well as a magnitude.)