Add a custom response header in ApiController

Question

Until now, I had a GET method that looked like the following:

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()      }); } 

This worked like a charm and it was good. However, I was told recently to send the response metadata (that is, Total, Count and Last properties) as response custom headers instead of the response body.

I cannot manage to access the Response from the ApiController. I thought of a filter or attribute, but how would I get the metadata values?

I can keep all this information on the response and then have a filter that will deserialize the response before being sent to the client, and create a new one with the headers, but that seems troublesome and bad.

Is there a way to add custom headers directly from this method on an ApiController?

Answer 1

You can explicitly add custom headers in a method like so:

[HttpGet] [Route("home/students")] public HttpResponseMessage GetStudents() {        // Get students from Database         // Create the response         var response = Request.CreateResponse(HttpStatusCode.OK, students);              // Set headers for paging         response.Headers.Add("X-Students-Total-Count", students.Count());                return response; } 

For more information read this article: http://www.jerriepelser.com/blog/paging-in-aspnet-webapi-http-headers/

Answer 2

I have entered comments, here is my complete answer.

You will need to create a custom filter and apply that to your controller .

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

In your Controller

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