✅ Item Returning Null From View Model??? Avalonia

Mek · 2024-03-09T05:33:18.348Z

MainWindowViewModel: https://pastebin.com/v5A0u9VJ TermsOfServiceViewModel: https://pastebin.com/BQx4qd1D I'm not understanding why when I click the run button to debug and run the program, that's when it deciedes to tell me that the model inside of the MainWindowViewModel's TermsOfService method cannot be null?

J

Jimmacle•3/9/24, 5:34 AM

what's the full error? with line numbers etc

M

MekOP•3/9/24, 5:36 AM

this is all it gives me but it's not until after I click the run button

J

Jimmacle•3/9/24, 5:38 AM

one of those methods has a parameter named

source

source

source

source that you're passing null to when you shouldn't

J

Jimmacle•3/9/24, 5:38 AM

(SetupModel)null

(SetupModel)null

(SetupModel)null

(SetupModel)null looks suspect to me

J

Jimmacle•3/9/24, 5:39 AM

and the reason it's "deciding" to tell you it's null at runtime is because it's a runtime error, not a compiler error

J

Jimmacle•3/9/24, 5:40 AM

it looks like you probably have compile time suggestions/hints about nullability, did you look at those?

M

MekOP•3/9/24, 5:40 AM

I don't know what those are or what they look like. apologies

JJimmacle it looks like you probably have compile time suggestions/hints about nullability...

M

MekOP•3/9/24, 5:42 AM

ok so getting ride of the

.Select(_ => (SetupModel)nul))

.Select(_ => (SetupModel)nul))

.Select(_ => (SetupModel)nul))

.Select(_ => (SetupModel)nul)) like fixed it. Thanks for your help

MMek I don't know what those are or what they look like. apologies

J

Jimmacle•3/9/24, 5:42 AM

the green squiggles

J

Jimmacle•3/9/24, 5:43 AM

you should do yourself a favor and add

<WarningsAsErrors>Nullable<WarningsAsErrors>

<WarningsAsErrors>Nullable<WarningsAsErrors>

<WarningsAsErrors>Nullable<WarningsAsErrors>

<WarningsAsErrors>Nullable<WarningsAsErrors> to your .csproj properties

J

Jimmacle•3/9/24, 5:43 AM

then code that has sketchy nullability won't compile in the first place

M

MekOP•3/9/24, 5:44 AM

where does it go in the csproj file?

M

MekOP•3/9/24, 5:46 AM

got it

M

MekOP•3/9/24, 5:47 AM

that's making everything error.

M

MekOP•3/9/24, 5:48 AM

internal bool GetSetupValue()
{
    var jsonData = JsonSerializer.Deserialize<SetupModel>(_setupPath);
    return jsonData.Setup;
}

internal bool UpdateSetup()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Setup = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

internal bool UpdateTos()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Tos = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

internal bool GetSetupValue()
{
    var jsonData = JsonSerializer.Deserialize<SetupModel>(_setupPath);
    return jsonData.Setup;
}

internal bool UpdateSetup()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Setup = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

internal bool UpdateTos()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Tos = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

internal bool GetSetupValue()
{
    var jsonData = JsonSerializer.Deserialize<SetupModel>(_setupPath);
    return jsonData.Setup;
}

internal bool UpdateSetup()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Setup = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

internal bool UpdateTos()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Tos = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

internal bool GetSetupValue()
{
    var jsonData = JsonSerializer.Deserialize<SetupModel>(_setupPath);
    return jsonData.Setup;
}

internal bool UpdateSetup()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Setup = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

internal bool UpdateTos()
{
    try
    {
        SetupModel setup = JsonSerializer.Deserialize<SetupModel>(_setupPath);
        setup.Tos = true;

        var updatedJsonData = JsonSerializer.Serialize(setup);

        File.WriteAllText(_setupPath, updatedJsonData);
        return true;
    }
    catch (Exception ex)
    {
        return false;
    }
}

every json serialization and it's usage beneath it is now an error

J

Jimmacle•3/9/24, 5:48 AM

then you have a lot of sketchy nullability

J

Jimmacle•3/9/24, 5:48 AM

as in, things that could be null that your code doesn't check for

M

MekOP•3/9/24, 5:48 AM

M

MekOP•3/9/24, 5:49 AM

J

Jimmacle•3/9/24, 5:49 AM

yes

J

Jimmacle•3/9/24, 5:49 AM

deserializing json may return null, but your code doesn't check for it

M

MekOP•3/9/24, 5:49 AM

they're all the same respectively

M

MekOP•3/9/24, 5:49 AM

so how do I fix it?

J

Jimmacle•3/9/24, 5:49 AM

which is a potential runtime crash

J

Jimmacle•3/9/24, 5:49 AM

by adding null checks

M

MekOP•3/9/24, 5:49 AM

ok I'll go research that

JJimmacle deserializing json may return null, but your code doesn't check for it

M

MekOP•3/9/24, 5:50 AM

so googling this, I found https://www.thomasclaudiushuber.com/2020/03/12/c-different-ways-to-check-for-null/ is that what you're talking about?

Thomas Claudius HuberThomas Claudius Huber

C#: Different ways to Check for Null

What is the classic way to check if for example a parameter value is null? If you've developed with C# since a while, you might be familiar with this classic syntax: public static int CountNumberOfSInName(string name) { if (name == null) { throw new ArgumentNullException(nameof(name));…

M

MekOP•3/9/24, 5:51 AM

if yes, then that means I need to build some type of universal error and exception handler

J

Jimmacle•3/9/24, 5:51 AM

that is the gist of it

J

Jimmacle•3/9/24, 5:51 AM

why does it mean that?

M

MekOP•3/9/24, 5:51 AM

I'd rather write once and re-use 100 times than to create new handlers in each file that is going to cause this problem

J

Jimmacle•3/9/24, 5:52 AM

the purpose of making nullable warnings errors is so you're forced to deal with them before they become NREs

M

MekOP•3/9/24, 5:52 AM

ok so then how would I properly deal with the ones that are erroring in this scenario?

J

Jimmacle•3/9/24, 5:52 AM

it depends what you want the behavior to be if the json deserializes to null

J

Jimmacle•3/9/24, 5:53 AM

do you want to return a default value? throw a more descriptive exception?

M

MekOP•3/9/24, 5:53 AM

I'd rather have it call the function to attempt to create the file and then recall itself to get the values it needs

J

Jimmacle•3/9/24, 5:54 AM

then that's what you should do

J

Jimmacle•3/9/24, 5:55 AM

keep in mind this is just the case where the contents of the file is literally the text

null

null

and doesn't account for other errors like the file not existing at all or containing invalid data

M

MekOP•3/9/24, 5:57 AM

so I tried to do this with handling a null value. It calls a function to handle what I'm wanting, however, I can't apply

&&

&&

&&

&& between a SetupModel and void, which I know, but I'm not sure what to do from here

J

Jimmacle•3/9/24, 5:59 AM

if you want to use the null coalescing operator then the right hand side has to return the same type as the left hand side

J

Jimmacle•3/9/24, 5:59 AM

if you don't want to return something from that method, you can't use that operator

M

MekOP•3/9/24, 5:59 AM

oh ok. I got you. one sec

M

MekOP•3/9/24, 6:00 AM

well nvm no i don't

J

Jimmacle•3/9/24, 6:00 AM

the only exception is if you wanted to throw an exception on the right hand side

JJimmacle the only exception is if you wanted to throw an exception on the right hand side

M

MekOP•3/9/24, 6:03 AM

right like

JsonSerializer.Deserialize<SetupModel>(_setupPath) ?? NullReferenceException;

JsonSerializer.Deserialize<SetupModel>(_setupPath) ?? NullReferenceException;

JsonSerializer.Deserialize<SetupModel>(_setupPath) ?? NullReferenceException;

JsonSerializer.Deserialize<SetupModel>(_setupPath) ?? NullReferenceException;, right?

J

Jimmacle•3/9/24, 6:03 AM

throw new MyException()

throw new MyException()

throw new MyException()

throw new MyException() but yeah

M

MekOP•3/9/24, 6:03 AM

would I be able to get away with something like

throw new NullReferenceException(HandleSetupException())

throw new NullReferenceException(HandleSetupException())

throw new NullReferenceException(HandleSetupException())

throw new NullReferenceException(HandleSetupException()) to have it trigger my function to do what I want it to do?

J

Jimmacle•3/9/24, 6:05 AM

no, that's not how exceptions work

M

MekOP•3/9/24, 6:05 AM

oh. I'm doing my best. promise

J

Jimmacle•3/9/24, 6:05 AM

throwing an exception basically means bailing out of the method immediately, and if it isn't caught by any calling code your program will just crash

✅ Item Returning Null From View Model??? Avalonia

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