Why nullable int (int?) doesn't increase the value via "+=" if the value is NULL?

Question

I have a page counter type of int?:

spot.ViewCount += 1;

It works ONLY if the value of ViewCount property is NOT NULL (any int).

Why the compiler do so?

I would be grateful for any solutions.

Answer 1

If you'll look into what compiler has produced for you then you'll see the internal logic behind.

The code:

int? i = null;
i += 1;

Is actually threated like:

int? nullable;
int? i = null;
int? nullable1 = i;
if (nullable1.HasValue)
{
    nullable = new int?(nullable1.GetValueOrDefault() + 1);
}
else
{
    int? nullable2 = null;
    nullable = nullable2;
}
i = nullable;

I used JustDecompile to get this code