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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(291.2, 54%, 38%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ECB%3C/text%3E%3C/svg%3E)
I am checking a property for null, but Visual Studio then warns me about a possibly null reference.
I am explicitly checking that the DisplayNames property is not null before enumerating it.
Please enlighten me as to what I am doing wrong, if anything.
Thank you.
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(92.8, 12%, 18%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EDL%3C/text%3E%3C/svg%3E)
Have you got a small example that anyone can use to reproduce this?
Try using a null-forgiving operator
Thank you, Viorel. You must be right about the analyser, because that works without any warning.
In order for me to mark this as correct, please post it as an answer. Please note that the property in the first line should be DisplayNames (plural).
Thanks for responding.
Karen, I'm not experienced enough to trust myself with this. The last time I used the null-forgiving operator to suppress a warning I got into a right mess. Maybe when I have greater knowledge I will be able to play the analyser.
Probably the analyser is not smart enough in this case. Maybe you can help it:
var names = vcards[i].DisplayName;
if( names != null )
{
foreach( var displayName in names )
. . .
Such subterfuge should not be necessary, if anyone has a simple example that reproduces the issue, it could be reported as a bug - so that hopefully such things get fixed.
David, here is a simple example that shows the problem.
internal class Program
{
static void Main(string[] args)
{
People p1 = new People();
People p2 = new People();
People p3 = new People();
List<People> Peoples = new List<People> { p1, p2, p3 };
for (var i = 0; i < Peoples.Count; i++)
{
if (Peoples[i].HumanList != null)
{
foreach (var human in Peoples[i].HumanList)
{
// Do something...
}
}
}
}
}
public class People
{
public List<Human?>? HumanList { get; set; }
public People()
{
HumanList = new List<Human?>
{
new Human("Bob"),
new Human("Mike")
};
}
}
public class Human
{
public Human(string name)
{
this.Name = name;
}
public string Name { get; set; }
}
This is how Visual Studio takes it:
That's great Charles. It repros with the latest VS Preview and .NET 7.
Would you report it as a bug using the Visual Studio "Report a Problem" facility and post a link back here to your report so that others can confirm & vote on it please.
Be sure to include the full minimal repro project and clear instructions (give the person processing the report an easy life so it doesn't get discarded), and possibly illustrate the fact that using a local reference does prevent the warning.
Reported.
Please see [https://developercommunity.visualstudio.com/t/Analyzer-reports-possibly-null-referenc/10261906
Thanks for doing that Charles.
For anyone interested, the C# experts reported that this is not a bug; rather it's the expected behaviour.
Thanks for taking the time to file this feedback issue. Unfortunately this is not a bug. The language is operating as intended here. Array element access, unlike property or field access, does not persist nullable state.
In order to persist the state of this check you can assign it out to another value:
if (array[i] is { } value) {
// value is non-null here
}
"operating as intended" - just not what anyone would intuitively expect (unless they have some deep internal knowledge).