WebApi 2返回类型

Question

我正在查看文档WebAPI 2,我对动作结果的构建方式感到非常失望.我真的希望有更好的方法.

所以文档说我可以返回这些:

**void**    Return empty 204 (No Content)

**HttpResponseMessage** Convert directly to an HTTP response message.

**IHttpActionResult**   Call ExecuteAsync to create an HttpResponseMessage, then convert to an HTTP response message.

**Other type**  Write the serialized return value into the response body; return 200 (OK).

我没有看到一个干净的方法来返回具有自定义HTTP状态代码,自定义标头和自动协商内容的项目数组.

我希望看到的是类似的东西

public HttpResult<Item> Post()
{
   var item = new Item();
   var result = new HttpResult<Item>(item, HttpStatusCode.Created);
   result.Headers.Add("header", "header value");

   return result;
}

这样我就可以浏览一个方法并立即看到返回的内容,并修改状态代码和标题.

我发现最接近的是NegotiatedContentResult<T>,带有奇怪的签名(为什么它需要一个控制器实例？),但是没有办法设置自定义头文件？

有没有更好的办法 ？

Answer 1

以下代码应该为您提供所需的一切:

[ResponseType(typeof(Item))]
public IHttpActionResult Post()
{
    var item = new Item();
    HttpContext.Current.Response.AddHeader("Header-Name", "Header Value");
    return Content(HttpStatusCode.Created, item);
}

...如果你真的需要返回一系列项目......

[ResponseType(typeof(List<Item>))]
public IHttpActionResult Post()
{
    var items = new List<Item>();
    // Do something to fill items here...
    HttpContext.Current.Response.AddHeader("Item-Count", items.Count.ToString());
    return Content(HttpStatusCode.Created, items);
}

Answer 2

我不认为web-api的设计者想要控制器方法摆弄标题.设计模式似乎是使用DelegatingHandler,ActionFilterAttribute和ApiController的ExecuteAsync可重写方法来处理身份验证和响应格式.

那么也许你应该在那里处理你的消息内容协商逻辑？

但是,如果您确实需要从控制器方法中控制标头,则可以进行一些设置以使其工作.为此,您可以创建自己的DelegationHandler,从"内部"响应标头转发所选标头:

public class MessageHandlerBranding : DelegatingHandler {
    protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var response = await base.SendAsync(request, cancellationToken);
        //If we want to forward headers from inner content we can do this:
        if (response.Content != null && response.Content.Headers.Any())
        {
            foreach (var hdr in response.Content.Headers)
            {
                var keyUpr = hdr.Key.ToUpper(); //Response will not tolerate setting of some header values
                if ( keyUpr != "CONTENT-TYPE" && keyUpr != "CONTENT-LENGTH")
                {
                    string val = hdr.Value.Any() ? hdr.Value.FirstOrDefault() : "";
                    response.Headers.Add(hdr.Key, val);                       
                }
            }
        }
        //Add our branding header to each response
        response.Headers.Add("X-Powered-By", "My product");
        return response;
    }  
}

然后在web-api配置中注册此处理程序,这通常在GlobalConfig.cs文件中.

config.MessageHandlers.Add(new MessageHandlerBranding());

您也可以为响应对象编写自己的自定义类,如下所示:

public class ApiQueryResult<T> : IHttpActionResult where T : class
{
    public ApiQueryResult(HttpRequestMessage request)
    {
        this.StatusCode = HttpStatusCode.OK; ;
        this.HeadersToAdd = new List<MyStringPair>();
        this.Request = request;
    }

    public HttpStatusCode StatusCode { get; set; }
    private List<MyStringPair> HeadersToAdd { get; set; }
    public T Content { get; set; }
    private HttpRequestMessage Request { get; set; }

    public void AddHeaders(string headerKey, string headerValue)
    {
        this.HeadersToAdd.Add(new MyStringPair(headerKey, headerValue));
    }

    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
    {
        var response = this.Request.CreateResponse<T>(this.StatusCode, this.Content);
        foreach (var hdr in this.HeadersToAdd)
        {
            response.Content.Headers.Add(hdr.key, hdr.value); 
        }
        return Task.FromResult(response);
    }


    private class MyStringPair
    {
        public MyStringPair(string key, string value)
        {
            this.key = key;
            this.value = value;
        }
        public string key;
        public string value;
    }
}

并在控制器中使用它:

 [HttpGet]
    public ApiQueryResult<CustomersView> CustomersViewsRow(int id)
    {
        var ret = new ApiQueryResult<CustomersView>(this.Request);
        ret.Content = this.BLL.GetOneCustomer(id);
        ret.AddHeaders("myCustomHkey","myCustomValue");
        return ret;
    }