Question

到目前为止，我有一个GET方法，如下所示：

protected override async Task<IHttpActionResult> GetAll(QueryData query)
{
     // ... Some operations

     //LINQ Expression based on the query parameters
     Expression<Func<Entity, bool>> queryExpression = BuildQueryExpression(query);

     //Begin to count all the entities in the repository
     Task<int> countingEntities = repo.CountAsync(queryExpression);

     //Reads an entity that will be the page start
     Entity start = await repo.ReadAsync(query.Start);

     //Reads all the entities starting from the start entity
     IEnumerable<Entity> found = await repo.BrowseAllAsync(start, queryExpression);

     //Truncates to page size
     found = found.Take(query.Size);

     //Number of entities returned in response
     int count = found.Count();

     //Number of total entities (without pagination)
     int total = await countingEntities;

     return Ok(new {
          Total = total,
          Count = count,
          Last = count > 0 ? GetEntityKey(found.Last()) : default(Key),
          Data = found.Select(e => IsResourceOwner(e) ? MapToOwnerDTO(e) : MapToDTO(e)).ToList()
     });
}

这就像一个魅力，它很好。但是，我最近被告知要将响应元数据（即Total，Count和Last属性）作为响应自定义标头而不是响应正文发送

我无法从ApiController访问Response。我想到了一个过滤器或属性，但我如何获取元数据值？

我可以在响应中保留所有这些信息，然后有一个过滤器，在将响应发送到客户端之前对其进行反序列化，并创建一个带有标题的新响应，但这看起来很麻烦和糟糕。

有没有办法在ApiController上直接从此方法添加自定义标题？

Answer 1

您可以在类似的方法中显式添加自定义标题：

[HttpGet]
[Route("home/students")]
public HttpResponseMessage GetStudents()
{
       // Get students from Database

       // Create the response
        var response = Request.CreateResponse(HttpStatusCode.OK, studends);

        // Set headers for paging
        response.Headers.Add("X-Students-Total-Count", studends.Count());

       return response;
}

有关详细信息，请阅读以下文章：http://www.jerriepelser.com/blog/paging-in-aspnet-webapi-http-headers/

Answer 2

我已经输入了评论，这是我的完整答案。

您需要创建自定义过滤器并将其应用于控制器。

public class CustomHeaderFilter : ActionFilterAttribute
{
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
       var count = actionExecutedContext.Request.Properties["Count"];
       actionExecutedContext.Response.Content.Headers.Add("totalHeader", count);
    }
}

在您的控制器

中

  public class AddressController : ApiController
        {
            public async Task<Address> Get()
            {
               Request.Properties["Count"] = "123";
            }
    }

Answer 3

您需要的是：

public async Task<IHttpActionResult> Get() 
{ 
    var response = Request.CreateResponse();
    response.Headers.Add("Lorem", "ipsum");

    return base.ResponseMessage(response); 
}

我希望这能回答你的问题。

Answer 4

简单的解决方案是：

HttpContext.Current.Response.Headers.Add("MaxRecords", "1000");

Answer 5

或者，如果您需要在每个响应中执行此操作，则最好利用DelegatingHandler。因为它将在请求/响应管道上运行，而不在控制器/操作级别上运行。就我而言，我必须在每个响应中添加一些标头，因此我做了我描述的事情。参见下面的代码段

public class Interceptor : DelegatingHandler
{
    protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var response = await base.SendAsync(request, cancellationToken);
        response.Headers.Add("Access-Control-Allow-Origin", "*");
        response.Headers.Add("Access-Control-Allow-Methods", "GET,POST,PATCH,DELETE,PUT,OPTIONS");
        response.Headers.Add("Access-Control-Allow-Headers", "Origin, Content-Type, X-Auth-Token, content-type");
        return response;
    }

}

您将需要在WebApiConfig中添加此处理程序

    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            config.MessageHandlers.Add(new Interceptor());
        }
    }

Answer 6

您可以使用自定义ActionFilter，它允许您发送自定义标头并访问HttpContext：

public class AddCustomHeaderFilter : ActionFilterAttribute
{
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
       actionExecutedContext.Response.Content.Headers.Add("name", "value");
    }
}

在ApiController

6 个答案: