C#•3y ago

❔ Why does this code give the CS8604 warning?

I'm confused why the below code gives the CS8604 warning. As far as I am concerned, I am null checking so it shouldn't appear. How can I improve it?

string? myString = null;

var stringIsEmpty = myString == null;

if (!stringIsEmpty)
{
    var reversedString = myString.Reverse();
    Console.WriteLine(reversedString);
}

string? myString = null;

var stringIsEmpty = myString == null;

if (!stringIsEmpty)
{
    var reversedString = myString.Reverse();
    Console.WriteLine(reversedString);
}

string? myString = null;

var stringIsEmpty = myString == null;

if (!stringIsEmpty)
{
    var reversedString = myString.Reverse();
    Console.WriteLine(reversedString);
}

string? myString = null;

var stringIsEmpty = myString == null;

if (!stringIsEmpty)
{
    var reversedString = myString.Reverse();
    Console.WriteLine(reversedString);
}

Thinker•2/2/23, 2:59 PM

Nullable flow analysis is not smart enough to figure that out when the result is stored in an intermediate variable.

Lexaro•2/2/23, 2:59 PM

Nullable flow analysis is not smart enough to figure that out when the result is stored in an intermediate variable.

Thinker•2/2/23, 3:00 PM

i'm getting more and more convinced you're a bot

Lexaro•2/2/23, 3:00 PM

i'm getting more and more convinced you're a bot

CChocohoop I'm confused why the below code gives the CS8604 warning. As far as I am concern...

Thinker•2/2/23, 3:00 PM

If you did if (myString != null)if (myString != null) or if (myString is not null)if (myString is not null) then it would pick up on it

Lexaro•2/2/23, 3:00 PM

If you did if (myString != null) or if (myString is not null) then it would pick up on it

ChocohoopOP•2/2/23, 3:09 PM

In my actual use case I've got some more complicated Boolean expressions and I need to name them something more self-documenting.

Thinker•2/2/23, 3:10 PM

Well, you can do myString!.Reverse()myString!.Reverse() which will force the compiler to just shut up because you know it won't be null

ChocohoopOP•2/2/23, 3:11 PM

For example var turnHasChanged = _turnLastTick != null && _turnLastTick != turnThisTick;var turnHasChanged = _turnLastTick != null && _turnLastTick != turnThisTick;

ChocohoopOP•2/2/23, 3:11 PM

Oh, that works!