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.net - .Net 6 没有运行两个以上的 HostedServices

问题描述

更新到 .Net 6 后，我的托管服务无法注册两个以上的托管服务：

System.InvalidOperationException
  HResult=0x80131509
  Message=Server has already started.
  Source=Microsoft.AspNetCore.Server.Kestrel.Core
  StackTrace:
   at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerImpl.<StartAsync>d__29`1.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.AspNetCore.Hosting.GenericWebHostService.<StartAsync>d__34.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable.ConfiguredTaskAwaiter.GetResult()
   at Microsoft.Extensions.Hosting.Internal.Host.<StartAsync>d__11.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable.ConfiguredTaskAwaiter.GetResult()
   at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.<RunAsync>d__4.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.<RunAsync>d__4.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.Run(IHost host)
   at Test.Program.Main(String[] args)

您可以重现它，创建一个新的 Blazor 服务器应用程序，然后添加三个空的后台服务，如下所示：

public class TestService1 : Microsoft.Extensions.Hosting.BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
    }
}

当我在启动类中添加两个以上的托管服务时，启动应用程序会崩溃，但上述异常除外。

services.AddHostedService<TestService1>();

有谁知道出了什么问题？我正在运行 .Net 6 Preview 5。

标签： .netblazor-server-side

解决方案

在做了更多研究之后，我发现了这个线程：https ://github.com/dotnet/core/blob/main/release-notes/6.0/known-issues.md#net-runtime 您可以使用以下解决方法，直到 Microsoft在下一个 .Net 预览版中修复了这个问题

Host.CreateDefaultBuilder(args)
.UseDefaultServiceProvider(o =>
{
    o.ValidateOnBuild = false;
});

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