How do i subscribe to onscroll event in Blazor?

After a couple of trials and errors, I decided to create a custom .net service that I register over on the js side. The service looks a something like this:

using System;
using Microsoft.JSInterop;

namespace myBlazorApp.Services
{
    public class ScrollInfoService: IScrollInfoService
    {
        public event EventHandler<int> OnScroll; 

        public ScrollInfoService(IJSRuntime jsRuntime)
        {
            RegisterServiceViaJsRuntime(jsRuntime);
        }

        private void RegisterServiceViaJsRuntime(IJSRuntime jsRuntime)
        {
            jsRuntime.InvokeVoidAsync("RegisterScrollInfoService", DotNetObjectReference.Create(this));
        }

        public int YValue { get; private set; }

        [JSInvokable("OnScroll")]
        public void JsOnScroll(int yValue)
        {
            YValue = yValue;
            Console.WriteLine("ScrollInfoService.OnScroll " + yValue);
            OnScroll?.Invoke(this, yValue);
        }
    }

    public interface IScrollInfoService
    {
         event EventHandler<int> OnScroll; 
         int YValue { get; }
    }
}

The service receives the onscroll event from the DOM and raises an event on the .net side. Here is what the script looks like on the js side:

window.onscroll = function() {
    if (window.scrollInfoService != null)
        window.scrollInfoService.invokeMethodAsync('OnScroll', window.pageYOffset);
}

window.RegisterScrollInfoService = (scrollInfoService) => {
    window.scrollInfoService = scrollInfoService;
}

I then inject my service in any Blazor component that needs it like this:

@using myBlazorApp.Services
@inject IScrollInfoService scrollInfoService
@implements IDisposable

<div>
     ...
</div>

@code {

    protected override void OnInitialized()
    {
        scrollInfoService.OnScroll += OnScroll;
    }

    private void OnScroll(object sender, int yValue)
    {
        DoSomething(yValue);
    }

    public void Dispose()
    {
        scrollInfoService.OnScroll -= OnScroll;
    }
}

This is how to get scrollTop for myDiv div via eval (weird but working) - see it in action on Blazor REPL.

@inject IJSRuntime JSRuntime;

<h1>DIV scrollTop: @ScrollTop</h1> 

<div id="myDiv" style="overflow:scroll; height:400px;" @onscroll="@OnScroll" >
      
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</div>

@code {
   public int ScrollTop { get; set; }

   private async Task OnScroll(EventArgs e)
   {
      ScrollTop = await JSRuntime.InvokeAsync<int>(
         "eval", "document.getElementById('myDiv').scrollTop");
   }
}

UPDATE: the similar way to do that but without using eval - thanks to Kristian Mariyanov. See it in action on Blazor REPL here - here you need to add JS custom function getScrollToTop to DOM window object:

<script>
  window.getScrollToTop =  (selector) => {
    return document.querySelector(selector).scrollTop
  }
</script>

and invoke it this way:

ScrollTop = await JS.InvokeAsync<int>("getScrollToTop", "#myDiv");

You can easily handle the Blazor OnScroll event by simply creating a Razor page that works as follows:

@page "/ScrollTest"
<h3>Scrolling</h3>

<div class="scroll" @onscroll="OnScroll">
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</div>
<div class="m-2 p-2">Scroll events: @counter</div>


<style>

    div.scroll {
        margin: 4px, 4px;
        padding: 4px;
        width: 500px;
        height: 110px;
        overflow-x: hidden;
        overflow-y: auto;
        text-align: justify;
    }
</style>

@code {

    private int counter;

    private void OnScroll()
    {
        counter++;
    }

}