我如何手动解析一个类型使用ASP。NET核心MVC内置依赖注入框架?
设置容器非常简单:
public void ConfigureServices(IServiceCollection services)
{
// ...
services.AddTransient<ISomeService, SomeConcreteService>();
}
但是如何在不执行注入的情况下解析ISomeService呢?例如，我想这样做:
ISomeService service = services.Resolve<ISomeService>();
在IServiceCollection中没有这样的方法。
当前回答
您可以使用IApplicationBuilder实例以这种方式注入依赖项
public void Configure(IApplicationBuilder app)
{
//---------- Your code
using (var serviceScope = app.ApplicationServices.GetRequiredService<IServiceScopeFactory>().CreateScope())
{
var resultLogic = serviceScope.ServiceProvider.GetService<IResultLogic>();
resultLogic.YourMethod();
}
//---------- Your code
}
其他回答
您可以使用IApplicationBuilder实例以这种方式注入依赖项
public void Configure(IApplicationBuilder app)
{
//---------- Your code
using (var serviceScope = app.ApplicationServices.GetRequiredService<IServiceScopeFactory>().CreateScope())
{
var resultLogic = serviceScope.ServiceProvider.GetService<IResultLogic>();
resultLogic.YourMethod();
}
//---------- Your code
}
您可以通过这种方式在诸如AuthorizeAttribute之类的属性中注入依赖项
var someservice = (ISomeService)context.HttpContext.RequestServices.GetService(typeof(ISomeService));
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton<ISelfServiceConfigLoad, SelfServiceConfigLoader>();
var sp = services.BuildServiceProvider();
var configservice = sp.GetServices<ISelfServiceConfigLoad>();
services.AddSingleton<IExtractor, ConfigExtractor>( sp =>
{
var con = sp.GetRequiredService<ISelfServiceConfigLoad>();
var config = con.Load();
return new ConfigExtractor(config.Result);
});
services.AddSingleton<IProcessor<EventMessage>, SelfServiceProcessor>();
services.AddTransient<ISolrPush, SolrDataPush>();
services.AddSingleton<IAPICaller<string, string>, ApiRestCaller<string, string>>();
services.AddSingleton<IDataRetriever<SelfServiceApiRequest, IDictionary<string, object>>, SelfServiceDataRetriever>();
}
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.AddDbContext<ConfigurationRepository>(options =>
options.UseSqlServer(Configuration.GetConnectionString("SqlConnectionString")));
services.AddScoped<IConfigurationBL, ConfigurationBL>();
services.AddScoped<IConfigurationRepository, ConfigurationRepository>();
}
我知道这是一个老问题，但我很惊讶，一个相当明显和恶心的黑客没有在这里。
您可以利用定义自己的ctor函数的能力，在定义服务时从服务中获取必要的值……显然，每次请求服务时都会运行此服务，除非您在利用ctor的第一个构造中显式地删除/清除并重新添加此服务的定义。
这种方法的优点是不需要您在服务配置期间构建或使用服务树。您仍然在定义如何配置服务。
public void ConfigureServices(IServiceCollection services)
{
//Prey this doesn't get GC'd or promote to a static class var
string? somevalue = null;
services.AddSingleton<IServiceINeedToUse, ServiceINeedToUse>(scope => {
//create service you need
var service = new ServiceINeedToUse(scope.GetService<IDependantService>())
//get the values you need
somevalue = somevalue ?? service.MyDirtyHack();
//return the instance
return service;
});
services.AddTransient<IOtherService, OtherService>(scope => {
//Explicitly ensuring the ctor function above is called, and also showcasing why this is an anti-pattern.
scope.GetService<IServiceINeedToUse>();
//TODO: Clean up both the IServiceINeedToUse and IOtherService configuration here, then somehow rebuild the service tree.
//Wow!
return new OtherService(somevalue);
});
}
修复这个模式的方法是让OtherService显式依赖于IServiceINeedToUse，而不是隐式依赖于它或它的方法的返回值…或者以其他方式显式地解决依赖关系。
