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, studends);

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

       return response;
}

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