Question: I don't get it. The `As` operator:

![The as operator is used to perform certain types of conversions between compatible reference or nullable types.](https://i.stack.imgur.com/T3JWd.jpg)

Then why does the following work?

```
struct Baby : ILive
{
    public int Foo { get; set; }

    public int Ggg() 
    {
        return Foo;
    }
}

interface ILive
{
    int Ggg();
}

void Main()
{
    ILive i = new Baby(){Foo = 1} as ILive;    // ??????
    Console.Write(i.Ggg());                    // Output: 1
}

```

* `Baby` is a struct, creating it will put value in `stack`. There is *no* reference involve here.
* There are certainly no nullable types here.

Any explanation as to why I'm wrong?

Answer: 
Casting it as an interface will create a boxed copy on the managed heap , and return a reference to the boxed copy. The box implements the interface.
You simply cast with reference type `ILive` nullable value, so no error is thrown. However if you try this commented code, you will get an error.

```
Baby b = new Baby ();
 object o = b;
//Baby bb = o as Baby ;

```

This is because you are trying to cast with `as` to value type and that can not be null.