管理咨询顾问是做什么的,淘宝怎么优化关键词步骤,网页制作工具三剑客,安卓html编辑器中文版可以只读的 ServiceCollectionIntro在 .NET 7 Preview 4 中#xff0c;ServiceCollection 可以声明为只读了#xff0c;这使得我们可以有效避免在构建了 ServiceProvider 之后再新增服务#xff0c;导致服务注册失败。Sample在新的版本中#xff0c;ServiceCollection 新增… 可以只读的 ServiceCollectionIntro在 .NET 7 Preview 4 中ServiceCollection 可以声明为只读了这使得我们可以有效避免在构建了 ServiceProvider 之后再新增服务导致服务注册失败。Sample在新的版本中ServiceCollection 新增了一个 MakeReadonly() 的 API调用之后ServiceCollection 就不能再修改了不能再注册新的服务或者移除集合中的服务再修改就会抛异常。直接来看一个示例吧示例代码如下var services new ServiceCollection();
services.AddSingletonIUserIdProvider, EnvironmentUserIdProvider();
await using (var provider services.BuildServiceProvider())
{Console.WriteLine(provider.GetRequiredServiceIUserIdProvider().GetHashCode());
}Console.WriteLine(services.IsReadOnly);services.MakeReadOnly();Console.WriteLine(services.IsReadOnly);try
{services.AddSingletonIHttpRequester, HttpClientHttpRequester();
}
catch (Exception ex)
{Console.WriteLine(ex);
}输出结果如下43942917
False
True
System.InvalidOperationException: The service collection cannot be modified because it is read-only.at Microsoft.Extensions.DependencyInjection.ServiceCollection.ThrowReadOnlyException()at Microsoft.Extensions.DependencyInjection.ServiceCollection.CheckReadOnly()at Microsoft.Extensions.DependencyInjection.ServiceCollection.System.Collections.Generic.ICollectionMicrosoft.Extensions.DependencyInjection.ServiceDescriptor.Add(ServiceDescriptor item)at Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.Add(IServiceCollection collection, Type serviceType, Type implementationType, ServiceLifetime lifetime)at Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddSingleton(IServiceCollection services, Type serviceType, Type implementationType)at Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddSingleton[TService,TImplementation](IServiceCollection services)at Net7Sample.ServiceCollectionSample.MainTest() in C:\projects\sources\SamplesInPractice\net7Sample\Net7Sample\ServiceCollectionSample.cs:line 28More在新的 HostApplicationBuilder 中也借助了这个 API 在构建 Host 的时候也会调用这个 API 来使得 ServiceCollection 中注册的服务不能再变更可以参考https://github.com/dotnet/runtime/pull/68051/files#diff-e55c31d683c37cca99b7a3a274beef4a3101d53b02c9ea989e4f6310094f68ec在我们的应用中遇到想要使 ServiceCollection 不能再修改的时候就可以考虑使用这个 API 来避免误操作从而导致意外的 BUGReferenceshttps://github.com/dotnet/runtime/pull/68051https://github.com/dotnet/runtime/pull/68051/files#diff-e55c31d683c37cca99b7a3a274beef4a3101d53b02c9ea989e4f6310094f68echttps://github.com/dotnet/runtime/issues/66126https://github.com/WeihanLi/SamplesInPractice/blob/master/net7Sample/Net7Sample/ServiceCollectionSample.cs.NET 7 中的 HostApplicationBuilder
