"Possible System.NullReferenceException" when using Null Conditional Operator
Hello, I'm seeing some weird behavior with the R# warning "Possible System.NullReferenceException"
HttpResponseMessage result = await Client.Post(url, value);
var resultContent = await result.Content?.ReadAsStringAsync();
I'm getting the warning on the result.Content property where I'm explicitly checking for null with the null-conditional operator '?.'
If I remove the operator then the warning goes away. So I'm not really sure what's happening here? Any advice or comments appreciated.
R# version 2019-05-01, VS version 14.0.25431.1
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The warning is correct - if result.Content is null, then you're trying to await a null Task, which will throw a NullReferenceException.
Ah, so when I remove the "?." R# is no longer able to detect if it will be null so it just doesn't show the warning, is that correct? Content can still hypothetically be null but R#'s null detection is just not able to accurately discover that.
Also thank you, learned something today.
By default, the "value analysis mode" is set to "optimistic":
https://www.jetbrains.com/help/resharper/Reference__Options__Code_Inspection__Settings.html
Therefore, if you don't test whether the Content property is null, R# assumes it's not.
https://www.jetbrains.com/help/resharper/Code_Analysis__Value_Analysis.html