InvalidOperationException Cannot modify ServiceCollection after application is built .Net6 异常

背景#

我用了一个叫Unchase.Swashbuckle.AspNetCore.Extensions的库来加强Swagger的文档，我一般写法是这样的：

builder.Services.AddSwaggerGen(c =>
            {
                //文档
                c.SwaggerDoc("v1", new OpenApiInfo
                {
                    Title = "『xxx』后端接口:myapi",
                    Version = "v1"
                });
                c.SwaggerDoc("v2", new OpenApiInfo { Title = "v2", Version = "v2" });
                c.MapType<long>(() => new OpenApiSchema { Type = "string" });

                //获取注释
                var apiXmlPath = Path.Combine(AppContext.BaseDirectory, $"{Assembly.GetExecutingAssembly().GetName().Name}.xml");
                c.IncludeXmlComments(apiXmlPath);

                c.DescribeAllParametersInCamelCase();                
                c.AddEnumsWithValuesFixFilters(services, o =>
                {
                    o.IncludeDescriptions = true;
                    o.IncludeXEnumRemarks = true;
                    o.DescriptionSource = DescriptionSources.DescriptionAttributesThenXmlComments;
                    o.IncludeXmlCommentsFrom(apiXmlPath);
                });
            });
 
...

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}
...

在.net core 3.1 和.net5 都运行好好的，在.net6就报异常：

InvalidOperationException: Cannot modify ServiceCollection after application is built.

System.InvalidOperationException: Cannot modify ServiceCollection after application is built.
   at Microsoft.AspNetCore.WebApplicationServiceCollection.CheckServicesAccess()
   at Microsoft.AspNetCore.WebApplicationServiceCollection.Add(ServiceDescriptor item)
   at Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddSingleton(IServiceCollection services, Type serviceType, Object implementationInstance)
   at Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddSingleton[TService](IServiceCollection services, TService implementationInstance)
   at Microsoft.Extensions.DependencyInjection.OptionsServiceCollectionExtensions.Configure[TOptions](IServiceCollection services, String name, Action`1 configureOptions)
   at Microsoft.Extensions.DependencyInjection.OptionsServiceCollectionExtensions.Configure[TOptions](IServiceCollection services, Action`1 configureOptions)
   at Unchase.Swashbuckle.AspNetCore.Extensions.Extensions.SwaggerGenOptionsExtensions.AddEnumsWithValuesFixFilters(SwaggerGenOptions swaggerGenOptions, IServiceCollection services, Action`1 configureOptions)
   at WebApi6._0.Bootstrapper.<>c__DisplayClass0_0.<AddSwagger>b__0(SwaggerGenOptions c) in D:\learn\netcoreTest\WebApi6.0\Bootstrapper.cs:line 32
   at Microsoft.Extensions.Options.ConfigureNamedOptions`1.Configure(String name, TOptions options)
   at Microsoft.Extensions.Options.OptionsFactory`1.Create(String name)
   at Microsoft.Extensions.Options.UnnamedOptionsManager`1.get_Value()
   at Swashbuckle.AspNetCore.SwaggerGen.ConfigureSwaggerGeneratorOptions..ctor(IOptions`1 swaggerGenOptionsAccessor, IServiceProvider serviceProvider, IWebHostEnvironment hostingEnv)
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Span`1& arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitIEnumerable(IEnumerableCallSite enumerableCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite callSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor(Type serviceType)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.SwaggerGenServiceCollectionExtensions.<>c.<AddSwaggerGen>b__0_1(IServiceProvider s)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass2_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
   at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.GetService(IServiceProvider sp, Type type, Type middleware)
   at lambda_method1(Closure , Object , HttpContext , IServiceProvider )
   at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass5_1.<UseMiddleware>b__2(HttpContext context)
   at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

下了源码下来发现，问题应该出现在这行：

...
c.AddEnumsWithValuesFixFilters(services, o =>
                {
                    o.IncludeDescriptions = true;
                    o.IncludeXEnumRemarks = true;
                    o.DescriptionSource = DescriptionSources.DescriptionAttributesThenXmlComments;
                    o.IncludeXmlCommentsFrom(apiXmlPath);
                });
...

对应nuget源码的这行：

   if (configureOptions != null)
   {
  		 services?.Configure(configureOptions);
   }

https://github.com/unchase/Unchase.Swashbuckle.AspNetCore.Extensions/blob/d710cb6557944c49824d0cb31b72b90ad0319c1f/src/Unchase.Swashbuckle.AspNetCore.Extensions/Extensions/SwaggerGenOptionsExtensions.cs#L82

原因是：.net6之后已经不允许在

var app = builder.Build();

app build后再做 services?.Configure()操作

那简单；

解决#

思路是，先在build操作之前就把services?.Configure()这种操作写好

所以我这里的写法可以改为：

1、先更换引用的nuget包(因为在作者修改这个问题前暂时打了一个自己的nuget)

<PackageReference Include="Unchase.Swashbuckle.AspNetCore.Extensions" Version="2.6.12" />

//改为
 <PackageReference Include="Hei.Unchase.Swashbuckle.AspNetCore.Extensions" Version="2.6.12.1" />

2、上面代码改为：

var apiXmlPath = Path.Combine(AppContext.BaseDirectory, $"{Assembly.GetExecutingAssembly().GetName().Name}.xml");
//这里提前
var action = new Action<FixEnumsOptions>(o =>
{
    o.IncludeDescriptions = true;
    o.IncludeXEnumRemarks = true;
    o.DescriptionSource = DescriptionSources.DescriptionAttributesThenXmlComments;
    o.IncludeXmlCommentsFrom(apiXmlPath);
});

services.AddSwaggerGen(c =>
{
    //文档
    c.SwaggerDoc("v1", new OpenApiInfo
    {
         Title = "『xxx』后端接口:myapi",
         Version = "v1",
    });
    c.SwaggerDoc("v2", new OpenApiInfo { Title = "v2", Version = "v2" });
    c.SwaggerDoc("v3", new OpenApiInfo { Title = "v3", Version = "v3" });
    c.SwaggerDoc("v4", new OpenApiInfo { Title = "华为服务号相关/健康币", Version = "v4" });
    c.MapType<long>(() => new OpenApiSchema { Type = "string" });
    c.IncludeXmlComments(apiXmlPath);
    c.DescribeAllParametersInCamelCase();
    //这里改为
    c.AddEnumsWithValuesFixFilters(action);
});