C#•2y ago

❔ Object reference not sent to an instance of an object

I have a WinUI3 app that uses C# and XAML, i'm attempting to foreach files. Files looks like this:

[ { "path": ".cache", 
    "type": "DIRECTORY" 
  }, 
  { "path": "Cargo.lock" 
  }, 
  { "path": "Cargo.toml" 
  } ]

[ { "path": ".cache", 
    "type": "DIRECTORY" 
  }, 
  { "path": "Cargo.lock" 
  }, 
  { "path": "Cargo.toml" 
  } ]

(not actual files, just mock data) But, when I create the NavigationViewItem with code, it gives me

Exception thrown: 'System.NullReferenceException' in MyProject.dll
Object reference not set to an instance of an object.

Exception thrown: 'System.NullReferenceException' in MyProject.dll
Object reference not set to an instance of an object.

Code:

                foreach (var file in files)
                {
                    await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
                    {
                        NavigationViewItem item1 = new NavigationViewItem();
                        item1.Content = file.Path;
                        item1.Tag = file.Path;
                        item1.Icon = new SymbolIcon(file.Type == Api.File.Types.Type.Regular ? Symbol.Page2 : Symbol.Folder);
                        nvSample.MenuItems.Add(item1);
                    });
                }

                foreach (var file in files)
                {
                    await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
                    {
                        NavigationViewItem item1 = new NavigationViewItem();
                        item1.Content = file.Path;
                        item1.Tag = file.Path;
                        item1.Icon = new SymbolIcon(file.Type == Api.File.Types.Type.Regular ? Symbol.Page2 : Symbol.Folder);
                        nvSample.MenuItems.Add(item1);
                    });
                }

23 Replies

HimmDawg•2y ago

You got a line for us?

AveryOP•2y ago

What do you mean? Like; where it's erroring?

HimmDawg•2y ago

Exactly

AveryOP•2y ago

I set some breakpoints, it said it's where i'm doing new NavigationViewItem

HimmDawg•2y ago

new NavigationViewItem()? That's.... interesting

AveryOP•2y ago

yeah

HimmDawg•2y ago

I'd say it is because you run it asynchronously in the Dispatcher

AveryOP•2y ago

I have to do that, because it won't let me create the nav items because different thread or whatever

HimmDawg•2y ago

Different thread? You can usually add MenuItems as easy as

var item = new NavigationViewItem()
{
    Content = "Foo",
    Tag = "Bar"
    // ...
};
NavigationView.MenuItems.Add(item);

var item = new NavigationViewItem()
{
    Content = "Foo",
    Tag = "Bar"
    // ...
};
NavigationView.MenuItems.Add(item);

AveryOP•2y ago

let me try that, with out the dispatcher

AveryOP•2y ago

HimmDawg•2y ago

Okay, but that means you are running the entire function in a different thread.

AveryOP•2y ago

yeah, when I receive a message from the websocket, it adds the item that's my intention if it's possible

HimmDawg•2y ago

Can we see more code? What I'd think is, that the NavigationViewItems should be created in the same thread, where the NavigationView was created and your socket just passes you the data for it

AveryOP•2y ago

Yeah, i'm creating the navigation view in the actual XAML. Not in the code. https://hastebin.skyra.pw/digojikiya.csharp had to find a hastebin service to upload the code to. too big for discord this is nvSample_Loaded_1

HimmDawg•2y ago

Hummm, in that case, passing data will be more difficult. Can you try the same approach with Dispatcher as before, but use

DispatcherQueue.TryEnqueue(() =>
{
  // create and add NavItems
});

DispatcherQueue.TryEnqueue(() =>
{
  // create and add NavItems
});

AveryOP•2y ago

holy, it works now tysm! everything works now, but i'm not sure if you'll be able to help me with another error.

        private async void MonacoEditor_NavigationCompleted(WebView2 sender, Microsoft.Web.WebView2.Core.CoreWebView2NavigationCompletedEventArgs args)
        {
            await Task.Delay(500); // Use asynchronous delay
            System.Diagnostics.Debug.WriteLine(fileContents);
            try
            {
                await MonacoEditor.ExecuteScriptAsync("monaco.editor.getModels()[0].setValue(\"" + fileContents + "\");");
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine("Script execution error: " + ex.Message);
            }

            System.Diagnostics.Debug.WriteLine("possibly set value");
        }

        private async void MonacoEditor_NavigationCompleted(WebView2 sender, Microsoft.Web.WebView2.Core.CoreWebView2NavigationCompletedEventArgs args)
        {
            await Task.Delay(500); // Use asynchronous delay
            System.Diagnostics.Debug.WriteLine(fileContents);
            try
            {
                await MonacoEditor.ExecuteScriptAsync("monaco.editor.getModels()[0].setValue(\"" + fileContents + "\");");
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine("Script execution error: " + ex.Message);
            }

            System.Diagnostics.Debug.WriteLine("possibly set value");
        }

The file contents logs, and the "possibly set value" also logs. But, the monaco script doesn't work. When I manually execute the JS in the devtools console, that appears to work; but the executescriptasync isn't doing anything. I did the task delay to wait for the editor to load once navigation was completed.

HimmDawg•2y ago

Ah, I never worked with MonacoEditor. So I probably cannot help

AveryOP•2y ago

MonacoEditor, is the WebView2; sorry

HimmDawg•2y ago

Do you have any way to check if the script was executed correctly?

AveryOP•2y ago

the value doesn't set the contents

HimmDawg•2y ago

Well, I am not sure what the script is referring to altogether. No clue what "monaco.editor.getModels()" is doing 😄. I cant help any further

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Object reference not sent to an instance of an object