Why must C# operator overloads be static?

Question

Why does C# require operator overloads to be static methods rather than member functions (like C++)? (Perhaps more specifically: what was the design motivation for this decision?)

Answer 1

This has been answered in excruciating detail by Eric Lippert in a blog post that has since been removed. Here is the archived version.

There is also another subtler point about value types and instance operators. Static operators make this kind of code possible:

class Blah {      int m_iVal;      public static Blah operator+ (Blah l, int intVal)     {         if(l == null)             l = new Blah();         l.m_iVal += intVal;         return l;     } }  //main Blah b = null; b = b + 5; 

So you can invoke the operator, even though the reference is null. This wouldn't be the case for instance operators.

Answer 2

Take a look at this post.

A couple of reasons, the primary seeming to be to preserve operator symmetry (such that the left hand side of a binary operation does not get special treatment, as being responsible for dispatching the operation).