generic NOT constraint where T : !IEnumerable

Question

As per the title, is it possible to declare type-negating constraints in c# 4 ?

Answer 1

one use for this would be an option type.

public class Option 
where A : !B
where B : !A
{
    private readonly A a;
    private readonly B b;

    private Option(){}

    public Option(A a) 
    {
        this.a = a
    }

    public Option(B b)  
    {
        this.b = b
    }
} 

runtime checking would of course work but you wouldn't have the benefit of type checking at compile time.