CODEWITHSUNDEEP
c#xamarin.formsblazor-webassemblyopenweathermap
Janos82
Janos82

Reputation: 21

Client side Blazor: Slow load of a resource

I have some lines of code, that worked well in Xamarin.Forms, but it performs very poorly in Client-side Blazor.

This is the code:
string s = System.Text.Encoding.UTF8.GetString(Properties.Resources.city_list); List _cityList = JsonConvert.DeserializeObject<List>(s).ToList();

the city_list is a huge list from OpenWeatherMap that is containing all the cities around the globe. Later I want to display this list as options in a select, so I would like to keep it on the client-side. The code now is very slow, it takes minutes to run it. Do you have an idea, how can I make it faster?

Thank you in advance Janos

Update: I removed the Take(20), because that is not part of the problem. I want to get the full list.

The city_list is a text file in Json format. I added it as Resource, so it is a byte array in this code.

Upvotes: 0

Views: 1191

Answers (1)

Barkin Kaplan
Barkin Kaplan

Reputation: 41

This problem is related to very slow string parsing in Blazor. Yesterday I hit the same problem with parsing a json data of 6 mb. Even with the small json data the delays between page landings are noticable to eye. In a non-Blazor .NET application parsing is done really fast though.

So I figured out whether the problem is about json parsing or in general string parsing. I tested the below code on a reguler Console app and on Blazor WebAssembly. The difference is huge: Console(768 milliseconds), Blazor 45(seconds). Seems like this is an issue with web assembly because javascript parsing is also fast. This problem has been around for sometime. See also here. https://github.com/dotnet/runtime/issues/40386

Well this being said even though this is a very simple problem it completely invalidates Blazor as a production ready framework.

This was tested on .NET 6 both for Console and Blazor.

public class StringParsePerfTest
{
    private string Text { get; set; } = "";
    public StringParsePerfTest()
    {
        for(int i = 0; i < 10000; i++)
        {
            if (i % 3 == 0) Text += "|";
            else Text += "a";
        }
    }

    public void Test()
    {
        var start = DateTime.Now;
        start= DateTime.Now;
        for(int i = 0; i < 10000; i++)
        {
            var splitted = Text.Split("|");
        }
        var end = DateTime.Now;
        Console.WriteLine($"{(end - start).TotalMilliseconds}");
    }
}

Upvotes: 1

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