订阅事件 c#

如果我没看错你的问题，你有一些后台进程捕获数据。此过程会在 中引发事件。因此，您必须注册为后台服务和 UI 的单一实例才能访问同一实例。EventsManagerIEventsMansger

由于您还在执行数据库操作，因此需要将它们与 分开。为此，可以在单独的作用域内或瞬态服务中处理数据库操作。该服务在 中注入并引发事件。IEventManagerIEventsManagerIEventsManager

下面是代码的重构版本。

各种对象。我在这里做了一些猜测。

public delegate void EventReceivedEvenHandler(EventsManager evManager, EventsView ev);

public interface IEventsManager
{
    public event EventReceivedEvenHandler EventReceived;
    public Task ProcessEvents(List<Telemetry> telemetryList, string deviceProtocolId);
    public void OnEventReceived(EventsView ev);
}

public class EventsManager : IEventsManager
{
    public event EventReceivedEvenHandler? EventReceived;

    public async Task ProcessEvents(List<Telemetry> telemetryList, string deviceProtocolId)
    {
        //Some async code...
        await Task.Yield();

        var eventView = new EventsView();
        OnEventReceived(eventView);
    }

    public virtual void OnEventReceived(EventsView ev)
    {
        EventReceived?.Invoke(this, ev);
    }
}

public class EventsView
{
    public string? Value { get; set; }
}

public class Telemetry { }

新服务：EventsHandler

namespace SO77374228.Data;

public class EventsHandler { 

    private IEventsManager _eventsManager;

    public EventsHandler(IEventsManager eventsManager)
    {
        _eventsManager = eventsManager;
        // get your Database stuff here
    }

    public async Task HandleEventAsync()
    {
        // Do your database saving here
        // You must use the DBContextFactory with using within the method to ensure correct handling of disposal of the context 
        await Task.Yield();
        //_eventsManager.ProcessEvents();
        _eventsManager.OnEventReceived(new() { Value = $"Hello at {DateTime.Now.ToLongTimeString()} " });
    }

}

服务注册：

builder.Services.AddSingleton<IEventsManager, EventsManager>();
builder.Services.AddTransient<EventsHandler>();

Index显示数据

@page "/"
@inject IEventsManager EventsManager
@implements IDisposable

<PageTitle>Index</PageTitle>

<h1>Hello, world!</h1>

Welcome to your new app.

<SurveyPrompt Title="How is Blazor working for you?" />

<div class="alert alert-primary">@_eventsView.Value</div>

@code {
    private EventsView _eventsView = new();

    protected override void OnInitialized()
        => this.EventsManager.EventReceived += this.OnEvent;

    private void OnEvent(object sender, EventsView eventsView)
    {
        _eventsView = eventsView;
        // as this is not a UI event we need to render the component to display any chnges
        this.InvokeAsync(this.StateHasChanged);
    }

    // Must Dispose properly
    public void Dispose()
        => this.EventsManager.EventReceived -= this.OnEvent;

}

并引发事件。Counter

@page "/counter"
@inject EventsHandler EventsHandler

<PageTitle>Counter</PageTitle>

<button class="btn btn-primary" @onclick="IncrementCount">Raise an Event</button>

@code {

    private async Task IncrementCount()
    {
        await this.EventsHandler.HandleEventAsync();
    }
}

这是一张图片，显示了两个浏览器窗口打开。单击该按钮，该事件将显示在另一个按钮中。