Using c# NULL coalescing operator with NOT NULL Scenarios

Question

I am populating a Class using LINQ and LinkUrl is a string property of my class.I need to set a value only if a property is not null , other wise no need to assign any values Currently The conditional operator ?: is used

    var formattedData = dataset.Select(p => new  ListModel
    {
        Prop1=....,
        Prop2=....,
        ...
        LinkUrl = string.IsNullOrWhiteSpace(p.LabelUrl) ? "" : "SET MY PROPERRTY TO A VALUE",
        .....
    }).ToList();

Can we replace this with C#‘s null-coalescing operator (??) or (?.) or something similar ??

Tne intention is to avoid the repeated use of assigning to "" in so many places

I can write it with operator ?? , but handle cases of NULL only like below .

    LinkUrl = p.LabelUrl ?? "SET MY PROPERRTY TO A VALUE"

Can we do something similar for Not null cases

If you use string.Empty instead of "", you never need to worry about assigning an empty string - it's free. The compiler always assigns the same instance, so that you don't waste any memory at all. — PMF
– PMF, Commented Feb 25, 2021 at 11:54
@PMF Strings are interned in C#, so assigning "" also reuses the same instance. — Johnathan Barclay
– Johnathan Barclay, Commented Feb 25, 2021 at 11:55
It appears you are right: stackoverflow.com/questions/263191/… I wasn't sure about this. — PMF
– PMF, Commented Feb 25, 2021 at 11:58
My intention in asking this question is to check any new features in c# available like ?? or ?. to replace the need of writing the logic on one side which is not necessary in this case . Looks like if we use ?: it is mandatory to write the logic for both if and else cases — Sebastian
– Sebastian, Commented Feb 25, 2021 at 12:08
I'm not sure what you actually want... if p.LabelUrl is null, your current code will replace it with "", but you say that you "need to set a value only if a property is not null" - which contradicts what your example code is actually doing. — Matthew Watson
– Matthew Watson, Commented Feb 25, 2021 at 12:10

Ivan Furdek · Accepted Answer · 2021-02-25 14:04:01Z

1

I think closest you could get to a shorthand for not null would be a set of extension methods

    public static T NullOrValue<T>(this T nullable, T value) where T : class => nullable == null ? null : value;
    
    public static T? NullOrValue<T>(this T? nullable, T value) where T : struct => nullable == null ? (T?)null : value;

Which would then be available on any nullable object as

var value = anyObjectOrNullable.NullOrValue(MyValue);

answered Feb 25, 2021 at 14:04

Ivan Furdek

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Paulo Morgado · Accepted Answer · 2021-02-25 14:45:24Z

0

You can use one of the Null-coalescing assignment.

But it won't check for empty strings.

answered Feb 25, 2021 at 14:45

Paulo Morgado

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3 Comments

Sebastian Over a year ago

Key req for me is to check the empty strings and i have to perform the actions only if the string is not empty

Paulo Morgado Over a year ago

Then, it has nothing to do with null coalescing, right?

Paulo Morgado Over a year ago

And you cannot conditionally assign in object initializers.

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