c# - Blazor WebAssembly；.net core SignalR Client；调用 HubConnectionBuilder.Builder() 时抛出 InvalidOperationException

Question

从此页面复制代码

Blazor 项目（.net 标准 2.1）

1. Microsoft.AspNetCore.Components.WebAssembly 3.2.1

2. Microsoft.AspNetCore.Components.WebAssembly.Build 3.2.1

3. Microsoft.AspNetCore.Components.WebAssembly.DevServer 3.2.1

4. Microsoft.AspNetCore.Http.Connections.Client 3.1.6

5. Microsoft.AspNetCore.SignalR.Client 3.1.6

6. Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson 3.1.6

7. System.Net.Http.Json 3.2.1

@code{
  private HubConnection HC;
  protected override async Task OnInitializedAsync(){
    HC = new HubConnectionBuilder().WithUrl("http://localhost:4000/class").Build();
    HC.On<string>("TextMessage", Message => Console.WriteLine(Message));
    await HC.StartAsync();
    await base.OnInitializedAsync();
  }
}

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asp.net core 服务器：（.net core 3.1）

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

     public IConfiguration Configuration { get; }
     public void ConfigureServices(IServiceCollection services){
         services.AddSingleton<ClassHub>();
         services.AddSignalR(o => {
             o.MaximumReceiveMessageSize = null;
             o.EnableDetailedErrors = true;
         });
     }
     public void Configure(IApplicationBuilder app, IWebHostEnvironment env){
         app.UseEndpoints(endpoints => {
             endpoints.MapHub<ClassHub>("/class", options => {
                 options.TransportMaxBufferSize = 256000;
                 options.ApplicationMaxBufferSize = 256000;
             });
         });
     }
 }

Answer 1

我有同样的错误。我在聊天中心使用 Blazor WebAssembly 和 ASP Api Rest。当我运行 Blazor 应用程序时，它崩溃了。我挣扎了很久，在谷歌上搜索。

但是我修复了它只是安装了一个 Nuget。确保Microsoft.AspNetCore.Http.Connections.Client已安装 Nuget。刚刚安装为 Nuget，就是这样。