Re: [1552] Possible Null Reference?

Hello,

The code builds with no errors or warnings.


Null reference problems are not detected by the C# compiler neither as errors
nor as warnings.

testing for null would remove the possibility of the null reference


Consider the following code:

if(Console.ReadLine().Length >= 3)
  str = Console.ReadLine().Substring(0, 3);

We could suppose that testing for length of three chars or above would remove
the possibility of an "index out of range" exception in the second line.
Luckily we know the semantic of the ReadLine method and would rather store
its value in a variable in any reallife code.

From the formal point of view, your sample is quite similar: ReSharper does
not know the semantics of the Element method, so it cannot assume the method
result does not change in time. Hence the warning.

Here we do not consider any threading issues (by convention, null reference
analysis assumes non-reentrant single-threaded execution and relies on users'
thread safety precautions -- otherwise there'd be tons of false alerts in
simple code), but just the nature of the method, in that it could behave
ReadLine()-like.

Should this method be a property with parameter (smth like root.Element["Dealer"]),
ReSharper would have assumed this code nullref-safe, because that's what
makes the difference between property semantics and method semantics. So
sad properties with parameters were dropped from C#.


Serge Baltic
JetBrains, Inc — http://www.jetbrains.com
“Develop with pleasure!”


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