Blazor 未接收在服务器端创建的信号器

Question

看了很多教程，例子，下面这个例子我在服务端调用，但是客户端收不到，有时能用有时不能（多用不着用）

应该很简单，但事实并非如此，任何建议都会对我有很大帮助！

服务器端

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers().AddNewtonsoftJson(options =>
        {
            options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
        });

        var connection = @"data source=comandai.database.windows.net;initial catalog=HojeTaPago;persist security info=True;user id=Comandai;password=Ck@21112009;MultipleActiveResultSets=True;";
        services.AddDbContext<ComandaiContext>(options => options.UseSqlServer(connection));

        services.AddSignalR(options => options.KeepAliveInterval = TimeSpan.FromSeconds(5));

        services.Configure<CookiePolicyOptions>(options =>
        {
            options.CheckConsentNeeded = context => true;
            options.MinimumSameSitePolicy = SameSiteMode.None;
        });

        services.AddResponseCompression(opts =>
        {
            opts.MimeTypes = ResponseCompressionDefaults.MimeTypes.Concat(
                new[] { "application/octet-stream" });
        });

        services.AddSwaggerGen(c =>
        {
            c.SwaggerDoc("v1", new OpenApiInfo { Title = "HojeTaPago API", Version = "v1" });
            c.AddSecurityDefinition("basic", new OpenApiSecurityScheme
            {
                Name = "Authorization",
                Type = SecuritySchemeType.Http,
                Scheme = "basic",
                In = ParameterLocation.Header,
                Description = "Basic Authorization header using the Bearer scheme."
            });

            c.AddSecurityRequirement(new OpenApiSecurityRequirement
            {
                {
                      new OpenApiSecurityScheme
                        {
                            Reference = new OpenApiReference
                            {
                                Type = ReferenceType.SecurityScheme,
                                Id = "basic"
                            }
                        },
                        new string[] {}
                }
            });
        });

        services.AddCors(options => options.AddPolicy("CorsPolicy",
        builder =>
        {
            builder.AllowAnyMethod().AllowAnyHeader()
                   .AllowCredentials();
        }));
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        app.UseResponseCompression();

        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        // Enable middleware to serve generated Swagger as a JSON endpoint.
        app.UseSwagger();

        // Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.),
        // specifying the Swagger JSON endpoint.
        app.UseSwaggerUI(c =>
        {
            c.SwaggerEndpoint("/swagger/v1/swagger.json", "HojeTaPago API V1");
            c.RoutePrefix = string.Empty;
        });

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseCors("CorsPolicy");

        app.UseAuthentication();

        app.UseAuthorization();

        app.UseMiddleware<AuthenticationMiddleware>();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapHub<NovoPedidoHub>("/novopedidohub");
            endpoints.MapControllers();
        });
    }
}

我在哪里使用信号器

await _novoPedidoContext.Clients.All.SendAsync("NovoPedido", ListaComandaItem);

客户端 - Blazor

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddRazorPages();
        services.AddServerSideBlazor();
        services.AddBlazoredLocalStorage();
        services.AddBootstrapCss();
        services.AddTransient<HubConnectionBuilder>();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseExceptionHandler("/Error");
            // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseStaticFiles();

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapBlazorHub();
            endpoints.MapFallbackToPage("/_Host");
        });
    }
}

我在哪里打电话..

protected override async Task OnInitializedAsync()
{
    DataService dataService = new DataService();
    PedidosParaAceitar = new List<Comanda>(await dataService.BuscarComandasAbertas());

    connection = _hubConnectionBuilder.WithUrl(dataService.servidor + "novopedidohub",
        opt =>
        {
            opt.Transports = HttpTransportType.WebSockets;
            opt.SkipNegotiation = true;
        }).Build();

    connection.On<List<ComandaItem>>("NovoPedido", async lista =>
    {
        var idEstabelecimento = await localStorage.GetItemAsync<int>("IdEstabelecimento");

        if (lista.FirstOrDefault().Comanda.IdEstabelecimento == idEstabelecimento)
        {
            if (PedidosParaAceitar == null)
                PedidosParaAceitar = new List<Comanda>();

            if (PedidosParaAceitar.Count(x => x.Id == lista.FirstOrDefault().IdComanda) > 0)
                foreach (var comandaitem in lista)
                {
                    PedidosParaAceitar.FirstOrDefault(x => x.Id == lista.FirstOrDefault().IdComanda).ComandaItem.Add(comandaitem);
                }
            else
                PedidosParaAceitar.Add(await dataService.BuscarComandaAberta(lista.FirstOrDefault().IdComanda));

            StateHasChanged();
        }
    });

    await connection.StartAsync();
}

Answer 1

您没有在标记中指定这是客户端 (WASM) 还是服务器端 Blazor。

看着问题我注意到ConfigureServices中的这一行：

services.AddServerSideBlazor();

因此，您正在尝试使用 SignalR，这是一个来自服务器的客户端通信库。在服务器端 Blazor 所有 C# 代码都在服务器上运行。在这方面，SignalR 是多余的，因为 Blazor 已经使用它在客户端和服务器之间进行通信。

非常幸运的巧合，我最近实际上编写了一个应用程序来测试这一点。我创建了一个服务器端 Blazor 应用，并编写了这个服务：

    public class TalkService
    {
        public TalkService()
        {
            history = new List<string>();
        }

        public Action<string> OnChange { get; set; }


        // inform all users of new message
        public Task SendAsync(string message)
        {
            // add to history
            history.Add(message);
            // ensure only last 10 shown
            if (history.Count > 10) history.RemoveAt(0);
            OnChange.Invoke(message);
            return Task.FromResult(0);
        }

        private readonly List<string> history;

        public IReadOnlyList<string> GetHistory() => history;
    }

然后我在服务器上将其注册为Singleton（所有客户端使用相同的服务） 在Startup.cs 中ConfigureServices() 方法中：

    services.AddSingleton<TalkService>();

然后将Index.razor改写如下：

@page "/"
@inject TalkService service

<p>Talk App started</p>

<p>Send a message: <input type="text"@bind="@message" />
    <button class="btn btn-sm btn-primary" @onclick="Send"  >Send</button>
    </p>

@foreach (var m in messages)
{
    <p>@m</p>
}
@code {
    string message;

    async Task Send()
    {
        if(!string.IsNullOrWhiteSpace(message))
            await service.SendAsync(message);
        message = string.Empty;
    }

    List<string> messages;

    protected override void OnParametersSet()
    {
        // load history
        messages = service.GetHistory().ToList();

        // register for updates
        service.OnChange += ChangeHandler;
    }

    protected void ChangeHandler(string message)
    {
        messages.Add(message);
        InvokeAsync(StateHasChanged);
    }
}

谈话服务当然是一个基本的“聊天”示例。它是一个单例，因此所有引用它的页面/客户端都使用相同的实例。该服务有一个简单的事件OnChange，客户端（如索引页面）可以在其他地方监听更改。

此应用不需要 SignalR，因为它已经在服务器端“存在”。

演示应用

演示应用还有一个后台服务，可以生成时间消息。我已将此推送到 GitHub 以作为指导：

https://github.com/conficient/BlazorServerWithSignalR