自托管ASPNET WebAPI中的MediaTypeFormatter问题 [英] MediaTypeFormatter issue in Self-Hosted ASPNET WebAPI

问题描述

我已经在SelfHosted AspNet WebAPI中实现了自定义MediaTypeFormatter.我已经使用Unity.WebApi进行依赖关系解析.控制器类仅知道由模型类实现的接口，而存储库则根据操作提供了具体的模型.

I have implemented a custom MediaTypeFormatter in a SelfHosted AspNet WebAPI. I've used Unity.WebApi for dependency resolution. The controller classes only know about the interfaces implemented by the model classes, whereas, repositories give the concrete models as a result of actions.

自定义MediaTypeFormatter继承自BufferedMediaTypeFormatter，如下所述:

The custom MediaTypeFormatter is inherited from BufferedMediaTypeFormatter as discussed here: http://www.asp.net/web-api/overview/formats-and-model-binding/media-formatters.

问题是此媒体类型格式化程序不起作用.即使我用来调试代码，也永远不会碰到ReadFormStream方法.有人知道吗?

The problem is this media type formatter is not working. Even when I use to debug the code, the ReadFormStream method is never hit. Does someone know:

1. 可能是什么问题?
2. 我需要告诉统一容器以将接口映射到模型类吗?
3. 如何在自定义媒体类型格式化程序中获取对依赖关系解析器的引用?

下面是添加格式化程序的代码:

Below is the code to add formatter:

var config = new SelfHostConfiguration("https://xxx.xxx.xxx.xxx:xxxx/");
config.Formatters.Add(new EntityTypeFormatter());

下面是EntityController的代码:

Below is the code for the EntityController:

    public class EntityController : ApiController
    {
        private readonly IEntitiesRepository repository = null;

        public EntityController(IEntitiesRepository repository)
        {
            if (repository == null)
            {
                throw new ArgumentNullException("repository");
            }

            this.repository = repository;
        }

        public IEnumerable<IEntity> Get()
        {
            return (IEnumerable<IEntity>)repository.Get();
        }
    }

下面是EntityRepository的代码:

Below is the code for the EntityRepository:

    public class EntitiesRepository : IEntitiesRepository
    {
        public IEnumerable<IEntity> Get()
        {
            return new Entities[]
            {
                new Entity
                { 
                    Prop1 = "value for property 1",
                    Prop2 = "value for property 2",
                    Prop3 = "value for property 3"
                },
                new Entity
                { 
                    Prop1 = "value for property 1",
                    Prop2 = "value for property 2",
                    Prop3 = "value for property 3"
                }
            };
        }
        public IEntity Get(long id)
        {
            return new Entity
                {
                    Prop1 = Convert.ToString(id),
                    Prop2 = "value for property 2",
                    Prop3 = "value for property 3"
                };
        }
    }

以下是EntityMediaTypeFormatter类的实现:

Below is the implementation of the EntityMediaTypeFormatter class:

public class EntityMediaTypeFormatter : BufferedMediaTypeFormatter 
    {
        public EntityMediaTypeFormatter()
            : base()
        {
            SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/xml"));
            SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
        }

        public override bool CanReadType(Type type)
        {
            if (type == null)
            {
                throw new ArgumentNullException("type");
            }

            if (type is IEntity)
            {
                return true;
            }
            else if (type.IsGenericType)
            {
                return type.GenericTypeArguments.Single(a => a.GetType().Equals(typeof(IEntity))) != null;
            }

            return false;
        }
        public override bool CanWriteType(Type type)
        {
            if (type == null)
            {
                throw new ArgumentNullException("type");
            }

            if (type is IEntity)
            {
                return true;
            }

            return false;
        }

        public override object ReadFromStream(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger)
        {
            if (type.IsInterface)
            {
                type = GetConcreteType(type);
            }

            return base.ReadFromStream(type, readStream, content, formatterLogger);
        }
        public override void WriteToStream(Type type, object value, Stream writeStream, HttpContent content)
        {
            //nothing special for now...
            base.WriteToStream(type, value, writeStream, content);
        }

        private Type GetConcreteType(Type type)
        {
            //TODO: Need to find a way to DependencyResolver to get the concrete type
            return typeof(Entity);
        }
    }

在此先感谢您的帮助.

Thanking in advance for any help.

推荐答案

在我看来，现有的格式化程序之一比您的格式化程序具有更高的优先级.在添加您的格式化程序集合之前，请先清除现有的格式化程序集合，或者将您的格式化程序集合插入位置0.

Looks to me like one of the existing formatters is taking priority over yours. Either clear the existing formatter collection before adding yours, or insert yours at position 0.

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