null!

LazyGuard · 2024-02-09T17:41:56.401Z

I am receiving some infos from an API and I have to decerialize to a model I am doing somthing like ```csharp if (response.IsSuccess) //deserialize to Person else // deserialize to ProblemDetails ``` And in person I hava defined properties using `public sting Name {get; set;} = null!` Is the use of ` null!` here a bad pratice ?

L

LazyGuardOP•2/9/24, 5:43 PM

I am asssuming that I will always have a Name in the response, if something happens and the API does change somehow it will result in an exception at runtime right ? I cannot be absoluetly sure about it being non null

L

LazyGuardOP•2/9/24, 5:43 PM

How to do better ?

L

LazyGuardOP•2/9/24, 5:45 PM

PS: t I have a lot more properties other than names How to do it in a scalable manner

L

LazyGuardOP•2/9/24, 5:46 PM

Any help ?

P

Pobiega•2/9/24, 5:47 PM

generally with modern C# you'd use

public required string Name {get; set;}

public required string Name {get; set;}

public required string Name {get; set;}

public required string Name {get; set;} instead

L

LazyGuardOP•2/9/24, 5:47 PM

yeah but we are not using that version in C# :/

P

Pobiega•2/9/24, 5:47 PM

then its fine

LLazyGuard I am asssuming that I will always have a Name in the response, if something happ...

P

Pobiega•2/9/24, 5:48 PM

well, then use a constructor, or validate the model after deserialization

L

LazyGuardOP•2/9/24, 5:49 PM

but it's in the model that I have that

null!

null!

null!

null! so if I recevie a

null

null

in Name, it will throws as soon as the deserialization process right ?

P

Pobiega•2/9/24, 5:49 PM

no

P

Pobiega•2/9/24, 5:49 PM

thats not what that does :p

P

Pobiega•2/9/24, 5:50 PM

null!

null!

null!

null! isnt magical, its just "set the value to null, and ignore the nullability warning"

M

MODiX•2/9/24, 5:50 PM

Angius

REPL Result: Success

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

Compile: 293.246ms | Execution: 34.872ms | React with ❌ to remove this embed.

P

Pobiega•2/9/24, 5:50 PM

that means if you deserialize something that doesnt set

Name

Name

Name

Name, it will still have the value of null.

A

Angius•2/9/24, 5:50 PM

As you can see, no errors

A

Angius•2/9/24, 5:50 PM

A person can be constructed without a name

L

LazyGuardOP•2/9/24, 5:51 PM

I am lost

I thought the

!

! throws whith

null

null

:/

P

Pobiega•2/9/24, 5:51 PM

no, its just a "ignore warning" thing

P

Pobiega•2/9/24, 5:51 PM

it sounds like you really want some validation

L

LazyGuardOP•2/9/24, 5:52 PM

yes ^^'

P

Pobiega•2/9/24, 5:52 PM

so add some validation, outside of the model

P

Pobiega•2/9/24, 5:52 PM

I'm not a big fan of models validating themselves, but its possible

P

Pobiega•2/9/24, 5:53 PM

json deserialization can support constructors, so you could do it there

P

Pobiega•2/9/24, 5:53 PM

that'd be fine

L

LazyGuardOP•2/9/24, 5:53 PM

okay thanks !

L

LazyGuardOP•2/9/24, 5:53 PM

by the way, what happen if there was a required there?

M

MODiX•2/9/24, 5:53 PM

Angius

REPL Result: Failure

class Person
{
    public required string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public required string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public required string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public required string Name { get; set; } = null!;
}

var p = new Person();

Exception: CompilationErrorException

- Required member 'Person.Name' must be set in the object initializer or attribute constructor.

- Required member 'Person.Name' must be set in the object initializer or attribute constructor.

- Required member 'Person.Name' must be set in the object initializer or attribute constructor.

- Required member 'Person.Name' must be set in the object initializer or attribute constructor.

Compile: 265.622ms | Execution: 0.000ms | React with ❌ to remove this embed.

M

MODiX•2/9/24, 5:55 PM

Pobiega

REPL Result: Failure

class Person
{
    public required string Name { get; set; }
}

var p = JsonSerializer.Deserialize<Person>("{}");

class Person
{
    public required string Name { get; set; }
}

var p = JsonSerializer.Deserialize<Person>("{}");

class Person
{
    public required string Name { get; set; }
}

var p = JsonSerializer.Deserialize<Person>("{}");

class Person
{
    public required string Name { get; set; }
}

var p = JsonSerializer.Deserialize<Person>("{}");

Exception: CompilationErrorException

- 'JsonSerializer' is an ambiguous reference between 'Newtonsoft.Json.JsonSerializer' and 'System.Text.Json.JsonSerializer'

- 'JsonSerializer' is an ambiguous reference between 'Newtonsoft.Json.JsonSerializer' and 'System.Text.Json.JsonSerializer'

- 'JsonSerializer' is an ambiguous reference between 'Newtonsoft.Json.JsonSerializer' and 'System.Text.Json.JsonSerializer'

- 'JsonSerializer' is an ambiguous reference between 'Newtonsoft.Json.JsonSerializer' and 'System.Text.Json.JsonSerializer'

Compile: 298.224ms | Execution: 0.000ms | React with ❌ to remove this embed.

P

Pobiega•2/9/24, 5:55 PM

Sigh

P

Pobiega•2/9/24, 5:56 PM

Unhandled exception. System.Text.Json.JsonException: JSON deserialization for type 'Person' was missing required properties, including the following: Name

P

Pobiega•2/9/24, 5:56 PM

thats what happens

P

Pobiega•2/9/24, 5:56 PM

STJ respects

required

required

required

required

MMODiX Empty message

L

LazyGuardOP•2/9/24, 5:57 PM

so to wrap up, the

null!

null!

null!

null! is a way to tell the compiler "it won't be null" . but if it happens to be

null

null

then nothing happens. Why not simply use

string?

string?

string?

string? there then

L

LazyGuardOP•2/9/24, 5:57 PM

it will have the same behaviour after all

L

LazyGuardOP•2/9/24, 5:57 PM

right ?

P

Pobiega•2/9/24, 6:01 PM

null!

null!

null!

null!, again, isnt magical

P

Pobiega•2/9/24, 6:01 PM

its essentially a workaround for nullability

P

Pobiega•2/9/24, 6:01 PM

its "make it null, but dont warn me about it, I know what I'm doing"

P

Pobiega•2/9/24, 6:01 PM

if you WANT the property to be nullable, and wont guarantee otherwise,

string?

string?

string?

string? is the correct thing to do

P

Pobiega•2/9/24, 6:01 PM

null!

null!

null!

null! is what we used before

required

required

required

required

A

Angius•2/9/24, 6:02 PM

x!

x!

x!

x! is a way of telling the compiler "trust me bro, I know

x

x can be

null

null

, but it isn't, I swear on me mum"

A

Angius•2/9/24, 6:02 PM

null!

null!

null!

null! therefore, is telling the compilert "trust me bro, this null ain't null"

P

Pobiega•2/9/24, 6:02 PM

and we all know swearing on your mum is a bad idea when you are lying

A

Angius•2/9/24, 6:02 PM

Which shuts up its warnings about uninitialized property

L

LazyGuardOP•2/9/24, 6:04 PM

yeah but I mean who cares, at the end of the day, whether it was

string

string

string

string and

null!

null!

null!

null! or

string?

string?

string?

string? it will have the same behaviour

P

Pobiega•2/9/24, 6:04 PM

.. no?

P

Pobiega•2/9/24, 6:04 PM

if you declare it as

string?

string?

string?

string?, then the consumer of your model will need to check for null before using the value

P

Pobiega•2/9/24, 6:04 PM

thats what NRTs are for

L

LazyGuardOP•2/9/24, 6:06 PM

okay I see, I was only having this examples in head

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public string Name { get; set; } = null!;
}

var p = new Person();

class Person
{
    public string? Name { get; set; };
}

var p = new Person();

class Person
{
    public string? Name { get; set; };
}

var p = new Person();

class Person
{
    public string? Name { get; set; };
}

var p = new Person();

class Person
{
    public string? Name { get; set; };
}

var p = new Person();

PPobiega if you declare it as `string?`, then the consumer of your model will need to che...

O

Only in .NET stacks do we trust•2/9/24, 6:20 PM

How about consuming legacy libraries where NRT has not been introduced, we still need to check non-nullable reference types too for null, right?

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