StateHasChanged()
在任意线程中调用是否安全?
让我给你提供一些背景信息。想象一个服务器端的 Blazor/Razor 组件应用程序,其中你有:
- 一个单例服务
NewsProvider
,它从任意线程触发BreakingNews
事件。 - 一个组件
News.cshtml
,该组件注入了该服务并订阅BreakingNews
事件。当事件被触发时,该组件会更新模型并调用StateHashChanged()
NewsProvider.cs
using System;
using System.Threading;
namespace BlazorServer.App
{
public class BreakingNewsEventArgs: EventArgs
{
public readonly string News;
public BreakingNewsEventArgs(string news)
{
this.News = news;
}
}
public interface INewsProvider
{
event EventHandler<BreakingNewsEventArgs> BreakingNews;
}
public class NewsProvider : INewsProvider, IDisposable
{
private int n = 0;
public event EventHandler<BreakingNewsEventArgs> BreakingNews;
private Timer timer;
public NewsProvider()
{
timer = new Timer(BroadCastBreakingNews, null, 10, 2000);
}
void BroadCastBreakingNews(object state)
{
BreakingNews?.Invoke(this, new BreakingNewsEventArgs("Noticia " + ++n));
}
public void Dispose()
{
timer.Dispose();
}
}
}
News.cshtml
@page "/news"
@inject INewsProvider NewsProvider
@implements IDisposable
<h1>News</h1>
@foreach (var n in this.news)
{
<p>@n</p>
}
@functions {
EventHandler<BreakingNewsEventArgs> breakingNewsEventHandler;
List<string> news = new List<string>();
protected override void OnInit()
{
base.OnInit();
breakingNewsEventHandler = new EventHandler<BreakingNewsEventArgs>(OnBreakingNews);
this.NewsProvider.BreakingNews += breakingNewsEventHandler;
}
void OnBreakingNews(object sender, BreakingNewsEventArgs e)
{
this.news.Add(e.News);
StateHasChanged();
}
public void Dispose()
{
this.NewsProvider.BreakingNews -= breakingNewsEventHandler;
}
}
Startup.cs
using Microsoft.AspNetCore.Blazor.Builder;
using Microsoft.Extensions.DependencyInjection;
using BlazorServer.App.Services;
namespace BlazorServer.App
{
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
// Since Blazor is running on the server, we can use an application service
// to read the forecast data.
services.AddSingleton<WeatherForecastService>();
services.AddSingleton<INewsProvider, NewsProvider>();
}
public void Configure(IBlazorApplicationBuilder app)
{
app.AddComponent<App>("app");
}
}
}
看起来是可以工作的,但我不确定StateHasChanged()
是否是线程安全的。如果不是,那么如何安全地调用StateHashChanged()
呢?是否有类似于Control.BeginInvoke
的东西?我应该使用SynchronizationContext.Post
吗?