處理 WebSocket 的 class 關閉和處置（Observable.Using）

Question

如何處理WebSocket的關閉和處置？ simple.SubscribeToTicker().Subscribe(...)也需要處理。

我看到有些人這樣做，但我不確定Observable.Using(...)的行為以及何時進行處置。

var message =
    Observable.Using(() => ws,
        _ => Observable.FromEventPattern<MessageReceivedEventArgs>(h => ws.MessageReceived += h,
            h => ws.MessageReceived -= h));

片段

using System.Net;
using System.Reactive.Linq;
using System.Text.Json;
using System.Text.Json.Serialization;
using RestSharp;
using WebSocket4Net;

namespace SimpleTest;

public class Simple
{
    public RestPriceTicker24Hr? GetTicker()
    {
        const string uri = "https://api.binance.com";

        var client = new RestClient(uri);
        var request = new RestRequest("/api/v3/ticker/24hr?symbol=BNBUSDT", Method.GET);
        var response = client.Execute(request);

        if (response.StatusCode != HttpStatusCode.OK)
            throw new InvalidOperationException();

        var content = response.Content;

        var deserialize = JsonSerializer.Deserialize<RestPriceTicker24Hr>(content, new JsonSerializerOptions
        {
            NumberHandling = JsonNumberHandling.AllowReadingFromString
        });

        return deserialize;
    }

    public IObservable<PriceTicker24Hr?> SubscribeToTicker()
    {
        const string uri = "wss://stream.binance.com:9443/ws";

        var ws = new WebSocket($"{uri}/bnbusdt@ticker") // TODO: Dispose
        {
            AutoSendPingInterval = 3, // 3 seconds
            EnableAutoSendPing = true
        };

        ws.Open();

        ws.Error += (_, e) => { Console.WriteLine($"Exception: {e.Exception.Message}"); };

        ws.Opened += (_, _) => { Console.WriteLine("Connection opened"); };

        ws.Closed += (_, _) => { Console.WriteLine("Connection closed"); };

        //var message =
        //    Observable.Using(() => ws,
        //        _ => Observable.FromEventPattern<MessageReceivedEventArgs>(h => ws.MessageReceived += h,
        //            h => ws.MessageReceived -= h));

        var message =
            Observable.FromEventPattern<MessageReceivedEventArgs>(h => ws.MessageReceived += h,
                h => ws.MessageReceived -= h);

        return message.Select(e =>
            JsonSerializer.Deserialize<PriceTicker24Hr>(e.EventArgs.Message, new JsonSerializerOptions
            {
                NumberHandling = JsonNumberHandling.AllowReadingFromString
            }));
    }
}

public class Program
{
    private static void GetData()
    {
        var simple = new Simple();

        var ticker = simple.GetTicker();
        simple.SubscribeToTicker().Subscribe(message => { Console.WriteLine($"Message: {message?.BestAskPrice}"); }); // TODO: Dispose
    }

    private static void Main()
    {
        GetData();

        Console.ReadKey();
    }
}

public class PriceTicker24Hr
{
    [JsonPropertyName("e")] public string? EventType { get; set; }

    [JsonPropertyName("E")] public long EventTime { get; set; }

    [JsonPropertyName("s")] public string? Symbol { get; set; }

    [JsonPropertyName("p")] public decimal PriceChange { get; set; }

    [JsonPropertyName("P")] public decimal PriceChangePercent { get; set; }

    [JsonPropertyName("w")] public decimal WeightedAveragePrice { get; set; }

    [JsonPropertyName("x")] public decimal PreviousClosePrice { get; set; }

    [JsonPropertyName("c")] public decimal LastPrice { get; set; }

    [JsonPropertyName("Q")] public decimal LastQuantity { get; set; }

    [JsonPropertyName("b")] public decimal BestBidPrice { get; set; }

    [JsonPropertyName("B")] public decimal BestBidQuantity { get; set; }

    [JsonPropertyName("a")] public decimal BestAskPrice { get; set; }

    [JsonPropertyName("A")] public decimal BestAskQuantity { get; set; }

    [JsonPropertyName("o")] public decimal OpenPrice { get; set; }

    [JsonPropertyName("h")] public decimal HighPrice { get; set; }

    [JsonPropertyName("l")] public decimal LowPrice { get; set; }

    [JsonPropertyName("v")] public decimal TotalTradedBaseVolume { get; set; }

    [JsonPropertyName("q")] public decimal TotalTradedQuoteVolume { get; set; }

    [JsonPropertyName("O")] public long OpenTime { get; set; }

    [JsonPropertyName("C")] public long CloseTime { get; set; }

    [JsonPropertyName("F")] public long FirstTradeId { get; set; }

    [JsonPropertyName("L")] public long LastTradeId { get; set; }

    [JsonPropertyName("n")] public long Count { get; set; }
}

public class RestPriceTicker24Hr
{
    [JsonPropertyName("symbol")] public string? Symbol { get; set; }
    [JsonPropertyName("priceChange")] public decimal PriceChange { get; set; }

    [JsonPropertyName("priceChangePercent")]
    public decimal PriceChangePercent { get; set; }

    [JsonPropertyName("weightedAvgPrice")] public decimal WeightedAveragePrice { get; set; }
    [JsonPropertyName("prevClosePrice")] public decimal PreviousClosePrice { get; set; }
    [JsonPropertyName("lastPrice")] public decimal LastPrice { get; set; }
    [JsonPropertyName("lastQty")] public decimal LastQuantity { get; set; }
    [JsonPropertyName("bidPrice")] public decimal BestBidPrice { get; set; }
    [JsonPropertyName("bidQty")] public decimal BestBidQuantity { get; set; }
    [JsonPropertyName("askPrice")] public decimal BestAskPrice { get; set; }
    [JsonPropertyName("askQty")] public decimal BestAskQuantity { get; set; }
    [JsonPropertyName("openPrice")] public decimal OpenPrice { get; set; }
    [JsonPropertyName("highPrice")] public decimal HighPrice { get; set; }
    [JsonPropertyName("lowPrice")] public decimal LowPrice { get; set; }
    [JsonPropertyName("volume")] public decimal TotalTradedBaseVolume { get; set; }
    [JsonPropertyName("quoteVolume")] public decimal TotalTradedQuoteVolume { get; set; }
    [JsonPropertyName("openTime")] public long OpenTime { get; set; }
    [JsonPropertyName("closeTime")] public long CloseTime { get; set; }
    [JsonPropertyName("firstId")] public long FirstTradeId { get; set; }
    [JsonPropertyName("lastId")] public long LastTradeId { get; set; }
    [JsonPropertyName("count")] public long Count { get; set; }
}

Answer 1

Every 確實需要在Observable.Using中，以便在可觀察對象結束時觸發處置。

這就是它的樣子：

public IObservable<PriceTicker24Hr?> SubscribeToTicker() =>
    Observable
        .Using(
            () =>
            {
                const string uri = "wss://stream.binance.com:9443/ws";
                var ws = new WebSocket($"{uri}/bnbusdt@ticker") // TODO: Dispose
                {
                    AutoSendPingInterval = 3, // 3 seconds
                    EnableAutoSendPing = true
                };
                ws.Open();
                ws.Error += (_, e) => { Console.WriteLine($"Exception: {e.Exception.Message}"); };
                ws.Opened += (_, _) => { Console.WriteLine("Connection opened"); };
                ws.Closed += (_, _) => { Console.WriteLine("Connection closed"); };
                return ws;
            },
            ws =>
                Observable
                    .FromEventPattern<MessageReceivedEventArgs>(
                        h => ws.MessageReceived += h,
                        h => ws.MessageReceived -= h)
                    .Select(e =>
                        JsonSerializer.Deserialize<PriceTicker24Hr>(
                            e.EventArgs.Message,
                            new JsonSerializerOptions
                            {
                                NumberHandling = JsonNumberHandling.AllowReadingFromString
                            })));

這是一個可測試的示例，可以看到Using in action：

IObservable<Unit> observable =
    Observable
        .Using(
            () => Disposable.Create(() => Console.WriteLine("Using Disposed!")),
            _ => Observable.Never<Unit>());
            
IDisposable subscription = observable.Subscribe();

subscription.Dispose();

彈出Using Disposed! 在控制台上。

這是另一個例子：

IObservable<int> observable =
    Observable
        .Using(
            () => Disposable.Create(() => Console.WriteLine("Using Disposed!")),
            _ => Observable.Repeat(42))
        .Take(1);
            
IDisposable subscription = observable.Subscribe(Console.WriteLine);

彈出以下內容：

42
Using Disposed!

希望這可以幫助您了解Observable.Using是如何工作的。