c# - 具有全局 Web API 过滤器属性的 Unity 依赖注入(inject)

Question

引用此 CodePlex unity article我能够使用 WebAPI Controller 获取过滤器属性，如下所示:

[MyFilterAttribute]
public class TestController : ApiController
{}

但是，如果我想在具有 GlobalConfiguration 的所有操作中应用我的过滤器属性，它会被剥离注入(inject)的依赖项:

public class MyFilterAttribute : ActionFilterAttribute 
{
    [Dependency]
    public MyDependency { get; set; }

    public override void OnActionExecuting(HttpActionContext actionContext)
    {
         if (this.MyDependency == null) //ALWAYS NULL ON GLOBAL CONFIGURATIONS
             throw new Exception();
    }
 }

public static class UnityWebApiActivator
    {
        public static void Start() 
        {
            var resolver = new UnityDependencyResolver(UnityConfig.GetConfiguredContainer());

            GlobalConfiguration.Configuration.DependencyResolver = resolver;

            GlobalConfiguration.Configuration.Filters.Add(new MyFilterAttribute());

            RegisterFilterProviders();
        }

        private static void RegisterFilterProviders()
        {
            var providers =
                GlobalConfiguration.Configuration.Services.GetFilterProviders().ToList();

            GlobalConfiguration.Configuration.Services.Add(
                typeof(System.Web.Http.Filters.IFilterProvider),
                new UnityActionFilterProvider(UnityConfig.GetConfiguredContainer()));

            var defaultprovider = providers.First(p => p is ActionDescriptorFilterProvider);

            GlobalConfiguration.Configuration.Services.Remove(
                typeof(System.Web.Http.Filters.IFilterProvider),
                defaultprovider);
        }
    }

有没有更好的地方可以添加全局配置？

Answer 1

出现问题是因为您要将新的 MyFilterAttribute 添加到过滤器集合(即:GlobalConfiguration.Configuration.Filters.Add(**new MyFilterAttribute()**))而不是通过 Unity 解决的实例。由于 Unity 不参与实例的创建，因此它没有注入(inject)依赖项的触发器。这应该可以通过简单地通过 Unity 解析实例来解决。例如:

GlobalConfiguration.Configuration.Filters.Add((MyFilterAttribute)resolver.GetService(typeof(MyFilterAttribute()));