Incorrect warning Converting null literal or possible null value to non-nullable type

Question

I try:

var err = (string)null;

(which I prefer to string? err=null;)

I get

warning CS8600: Converting null literal or possible null value to non-nullable type.

But the type of err is correctly set to a nullable string as is evident by hovering over it in visual studio.

Is this warning a dud ?

Sweeper · Accepted Answer · 2021-09-06 04:46:40Z

6

Assuming you have nullable reference types turned on, the warning is correctly pointing out that you are casting null to a non-nullable type - string. It is not about the type of err being non-nullable. err is nullable, as vars always are.

If you cast to string? instead, which is nullable, then the warning goes away:

var err = (string?)null;

edited Sep 6, 2021 at 4:46

answered Sep 6, 2021 at 4:43

Sweeper

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