Click me

@code {

    public async Task HandleClick()
    {
        await Task.Run(()=> System.Threading.Thread.Sleep(1000));
    }

    protected override void OnAfterRender(bool firstRender)
    {
        Console.WriteLine("Rendered");
    }
}

if(firstRender)
{
   // Call JSInterop to initialize your js functions, etc.
   // This code will execute only once in the component life cycle.
   // The variable firstRender is true only after the first rendering of the
   // component; that is, after the component has been created and initialized.
   // Now, when you click the div element firstRender is false, but still the
   // component is rendered twice, before the awaited method (Task.Run) is called,
   // and after the awaited method completes. The first render occurs because UI
   // event automatically invoke the StateHasChanged method. The second render
   // occurs also automatically after an awaited method in an async method
   // completes. This is how Blazor works, and it shouldn't bother you.
}