C#•2y ago

✅ Unsure of how to fix these avalonia errors

Object reference not set to an instance of an object -> LoginView.axaml
Unable to resolve type SplashViewModel from namespace using:SplashScreen.ViewModels -> Splash.axaml
Object reference not set to an instance of an object -> UpdateAvailableView.axaml

Object reference not set to an instance of an object -> LoginView.axaml
Unable to resolve type SplashViewModel from namespace using:SplashScreen.ViewModels -> Splash.axaml
Object reference not set to an instance of an object -> UpdateAvailableView.axaml

Object reference not set to an instance of an object -> LoginView.axaml
Unable to resolve type SplashViewModel from namespace using:SplashScreen.ViewModels -> Splash.axaml
Object reference not set to an instance of an object -> UpdateAvailableView.axaml

Object reference not set to an instance of an object -> LoginView.axaml
Unable to resolve type SplashViewModel from namespace using:SplashScreen.ViewModels -> Splash.axaml
Object reference not set to an instance of an object -> UpdateAvailableView.axaml

LoginView.axaml: https://pastebin.com/Kb0resSx
LoginViewMode.cs: https://pastebin.com/BcuyxF5S
Splash.axaml: https://pastebin.com/iazXwshx
SplashViewModel.cs: https://pastebin.com/U1FEwwSU
UpdateAvailableView.axaml: https://pastebin.com/C9WhCRC5
UpdateAvailableViewModel.cs: https://pastebin.com/p2mT7zt2

I spent a vast majority of yesterday trying to avoid asking for assistance with these problems and tried fixing them on my own. I get these errors in my Error List in visual studio. When I try running my program, it launches, but it's just a black screen and I'm not sure how to fix these problem. Thanks

Klarth•2/27/24, 5:49 AM

If it launches, there are probably ghost errors. It happens sometimes because XAML has its own tooling that's separate from C#'s. You can double check by checking the Output tab in VS to see if the build really failed. If it was successful, just ignore the errors. You need to restart VS to get rid of them, usually.

Klarth•2/27/24, 5:51 AM

Not sure about the black screen issue. It's hard to debug multiple file systems without knowing exactly which view is black. Easier if it were on GitHub so somebody could clone + run locally.

KKlarth Not sure about the black screen issue. It's hard to debug multiple file systems ...

MekOP•2/27/24, 11:15 AM

It is on GitHub. https://github.com/mekasu0124/Diary

GitHub

GitHub - mekasu0124/Diary: A general use diary with the option to s...

A general use diary with the option to store your data locally or in online storage - mekasu0124/Diary

Klarth•2/27/24, 2:42 PM

You baked in way too many bugs within testing. I really have no idea how you got this far.

Klarth•2/27/24, 2:44 PM

You used `async` in a constructor which silently fails. Do not do this. Instead:```cspublic MainWindowViewModel(Database db, GithubService gvs, Helpers hp){ _db = db; _gvs = gvs; _hp = hp;}```And call your async method from code-behind:```cspublic partial class MainWindowView : Window{ public MainWindowViewModel ViewModel => (MainWindowViewModel)DataContext!; public MainWindowView() { InitializeComponent(); } protected override async void OnLoaded(RoutedEventArgs e) // Yes this needs to be async void { await ViewModel.CheckForUpdate(); }}```

Klarth•2/27/24, 2:45 PM

You have no ViewLocator, so your Views won't be found from your ViewModels anyways. You can either add the ViewLocator or do this in App.axaml:```xml<Application x:Class="Diary.App" xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:v="using:Diary.Views" xmlns:vm="using:Diary.ViewModels" RequestedThemeVariant="Default">  <Application.Styles> <FluentTheme /> </Application.Styles> <Application.DataTemplates> <DataTemplate x:DataType="vm:LoginViewModel"> <v:LoginView /> </DataTemplate> <DataTemplate x:DataType="vm:UpdateAvailableViewModel"> <v:UpdateAvailableView /> </DataTemplate> </Application.DataTemplates></Application>```

Klarth•2/27/24, 2:46 PM

At this point, I'm getting exceptions because I don't have the necessary files, so I can't diagnose any further.

Klarth•2/27/24, 2:47 PM

This observable merging seems like a bad idea, but I don't use RxUI:

    public void UpdateScreen(VersionData version)
    {
        var vm = new UpdateAvailableViewModel(version, CurrentUser);

        Observable.Merge(vm.GoHome)
            .Take(1)
            .Subscribe(model =>
            {
                if (model == null)
                {
                    LoginScreen();
                }
            });

        Content = vm;
    }

    public void UpdateScreen(VersionData version)
    {
        var vm = new UpdateAvailableViewModel(version, CurrentUser);

        Observable.Merge(vm.GoHome)
            .Take(1)
            .Subscribe(model =>
            {
                if (model == null)
                {
                    LoginScreen();
                }
            });

        Content = vm;
    }

Klarth•2/27/24, 2:49 PM

Your csproj also has this which prevents nesting of

MainWindowView

MainWindowView

in the Solution Explorer:

<ItemGroup>
  <Compile Update="Views\MainWindowView.axaml.cs">
    <DependentUpon>MainWindowView.axaml</DependentUpon>
  </Compile>
</ItemGroup>

<ItemGroup>
  <Compile Update="Views\MainWindowView.axaml.cs">
    <DependentUpon>MainWindowView.axaml</DependentUpon>
  </Compile>
</ItemGroup>

MekOP•2/27/24, 3:09 PM

Oh wow. So i just got a lot of it backwards and didn’t even realize it. Aside from the view locator, I’ve been doing everything else the same across multiple projects. Hm. Ok. I’ll have to do some rewriting when I get home from work. Another question for you. I’m wanting to build my apps for offline use as well. Like a hybrid type thing. I want to create a function or a class (whichever is better) that I can call from app.axaml.cs. It basically check if the user is connected to internet. If so, it’ll use an online dabatase. Otherwise, it’ll use SQLite with a local database instead and then when the user connects to internet again in the future, it’ll push all their locally saved progress to the online database

MMek Oh wow. So i just got a lot of it backwards and didn’t even realize it. Aside fr...

Klarth•2/27/24, 3:25 PM

There's no way to reliably check internet connection without making a request. You could create an endpoint to ping for a fast response on startup, otherwise you need to fallback when the connection times out (manually adding this to the task).

Alternatively, you could work the other way around: host locally by default and sync to the online API periodically. You won't need intensive fallback handling to offline mode on every request this way.

Klarth•2/27/24, 3:26 PM

If you're using a REST client like https://github.com/reactiveui/refit, it will let you configure a timeout in one spot for all requests.

KKlarth If you're using a REST client like <https://github.com/reactiveui/refit>, it wil...

MekOP•2/27/24, 4:28 PM

Great advice. Ty. I’m using a FastAPI for this project if that helps

MekOP•2/27/24, 5:50 PM

With FastAPI don’t I have to use something called UUID

Klarth•2/27/24, 5:54 PM

Oh, Python stuff. No idea if it has a client generator. Otherwise, you need to create the client with types and endpoints yourself on the C# side so you can actually communicate with the API. Refit helps with that if you need to build it yourself.

MekOP•2/27/24, 6:06 PM

This is how I use the FastAPI on my websites. I’m assuming it would be similar? Probably not. I’ll have to look up how to use FastAPI with a C# Avalonia desktop app

Klarth•2/27/24, 6:16 PM

That looks poorly maintainable. Having a function that mixes API access, serialization, data transforms, and defining the storage schema which apparently just is supposed to leak to the caller?

Klarth•2/27/24, 6:17 PM

.NET is strongly typed, so you create Models to store the data. Either classes or records, but records are easier to define. The property names in the Model match the JSON schema, so System.Text.Json will let you map it in a single call. Data transforms are less straightforward.

KKlarth That looks poorly maintainable. Having a function that mixes API access, seriali...

MekOP•2/27/24, 11:37 PM

Which part? The Python or the JavaScript?

Klarth•2/27/24, 11:38 PM

"Yes"

KKlarth .NET is strongly typed, so you create Models to store the data. Either classes o...

MekOP•2/27/24, 11:38 PM

Right. I’ll be using a json file for the config file. It’ll have a setup Boolean, and it’ll hold the users settings that they adjust through the settings menu

Klarth•2/27/24, 11:39 PM

Obvious bias because I'm used to writing in C#. :catlul:

KKlarth "Yes"

MekOP•2/27/24, 11:40 PM

So the Java script is the React API. That’s how it’s used and that’s how everyone who’s helped me with my code used it too. I don’t know enough about JS to do anything more than put stuff on the screen. As far as the Python goes, all that function is doing is reading in the information from the json file. It’s going to create a new Project model and then put them all in a list and return it back to the Java script code

Klarth•2/27/24, 11:40 PM

The JS side is certainly the worse of the two.

KKlarth Obvious bias because I'm used to writing in C#. :catlul:

MekOP•2/27/24, 11:40 PM

True lol but I always use json files that are locally hosted to store the setup Boolean and other items needed from the user that don’t need to go anywhere past local host

KKlarth The JS side is certainly the worse of the two.

MekOP•2/27/24, 11:41 PM

It’s ReactJS. lol to my knowledge, and I could always be wrong, they do it like that in the docs too

Klarth•2/27/24, 11:43 PM

I know. The examples (and JS as a whole) will just DIY the schema definition in code (functions) instead of creating concrete type definitions.

MekOP•2/27/24, 11:44 PM

Understandable. The only thing I hate about C# that I love about Python is the type definitions. If I have x = 9, it should be smart enough to know that’s an integer lol but that’s just my opinion

Klarth•2/27/24, 11:45 PM

var x = 9;

var x = 9;

good enough

Klarth•2/27/24, 11:46 PM

And you keep strong typing, don't need type hints, etc.

MekOP•2/27/24, 11:49 PM

Idk I just don’t feel “natural” using var lmao

Klarth•2/27/24, 11:52 PM

I always use an explicit type for numerics, but that's possibly from long-ingrained habits.

MekOP•2/27/24, 11:52 PM

everyone has their own way of doing things, and that's what makes us unique

Klarth•2/27/24, 11:53 PM

Classes and structs? Almost never outside of needing to define something and initialize later.

MekOP•2/27/24, 11:53 PM

ok. just got to my computer. going back up and starting re-writes

KKlarth Classes and structs? Almost never outside of needing to define something and ini...

MekOP•2/27/24, 11:54 PM

that's what I like about Python, although different, to me they're the same

class MyClass:
  def __init__(self):
    self.username = ""
    self.password = ""

class MyClass:
  def __init__(self):
    self.username = ""
    self.password = ""

public class MyClass()
{
  private string _username;
  private string _password;
}

public class MyClass()
{
  private string _username;
  private string _password;
}

MekOP•2/27/24, 11:54 PM

corrected*

Klarth•2/27/24, 11:55 PM

C# version's members aren't accessible anywhere.

Klarth•2/27/24, 11:55 PM

public record MyClass(string UserName, string Password);

public record MyClass(string UserName, string Password);

Klarth•2/27/24, 11:56 PM

Is the better way to define classes that are data-only (no behavior).

KKlarth 1. You used `async` in a constructor which silently fails. Do not do this. Inste...

MekOP•2/28/24, 12:02 AM

You used
async
async
in your constructor which silently fails. Do not do this, instead:
<code>

Right. It silently fails because I did not await the call. I didn't await the call because I didn't want to make the constructor async, however, I will give your method a try.

You have no ViewLocator, so your Views won't be found from your ViewModels anyways. You can either add the ViewLocator or do this in App.axaml:
<code>

My GradeBook application doesn't have a ViewLocator file either, and it runs perfectly fine. https://github.com/mekasu0124/GradeBook

This observable merging seems like a bad idea, but I don't use RxUI:
<code>
Your csproj also has this which prevents nesting of MainWindowView in the solution explorer:
<code>

I'll look into this, but it helps me to keep the MainWindowView in the View folder and same for MainWindowViewModel too.

Alternatively, you could work the other way around: host locally by default and sync to the online API periodically. You won't need intensive fallback handling to offline mode on every request this way. If you're using a REST client like <link>, it will let you configure a timeout in one spot for all requests

I'm interested in learning more about this and possibly seeing some code examples too please?

MMek > 1. You used `async` in your constructor which silently fails. Do not do this, ...

Klarth•2/28/24, 12:10 AM

I don't see any way that project could work to resolve views. There don't seem to be any
```
DataTemplate
```
```
DataTemplate
```
s nor is there a ViewLocator.

Klarth•2/28/24, 12:11 AM

I can't really give Refit examples. I've tried it once on an API that I had a serious blocker on, so I ended up not being able to use said API. It was much nicer than using

HttpClient

HttpClient

RestSharp

RestSharp

though.

MekOP•2/28/24, 12:12 AM

ok I'll look up a tutorial for that

Klarth•2/28/24, 12:12 AM

There are some basic docs and plenty of examples if you GitHub search for relevant methods / classes like

RestService.For

RestService.For

Klarth•2/28/24, 12:14 AM

(The blocker was related to OAuth and requiring actual written permissions for a manually created account, so nothing limited by Refit itself. The API had changed since I last tried)

KKlarth 2. I don't see any way that project could work to resolve views. There don't see...

MekOP•2/28/24, 12:17 AM

both projects have a ViewModelBase.cs file in the VIewModels folder, but they don't have a ViewLocator file and I went to restore some repo's from old projects to look at them, but GitHub cleaned out the deleted list so that's a bust. I'm just going to create a new blank project, and see if it comes with one

MekOP•2/28/24, 12:19 AM

yea see it doesn't come with anymore since they changed how the project is created. Used too, you would select one of the options for an Avalonia project (desktop, web, mobile) in the menu when creating the project, but they changed it and I guess it doesn't come with it anymore

MMek both projects have a ViewModelBase.cs file in the VIewModels folder, but they do...

Klarth•2/28/24, 12:20 AM

I've been seeing the

.Desktop

.Desktop

project created lately across other people. Which project template is that, specifically?

MekOP•2/28/24, 12:22 AM

the only one that avalonia has available to my knowledge and at the end I select compiled bindings and that's the setup process now since I last updated VS and this changed happened along with it so I'm assuming its set to the latest version of avalonia

✅ Unsure of how to fix these avalonia errors

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