Can't set Content-Type header on HttpResponseMessage headers?
I'm using the ASP.NET WebApi. I'm creating a PUT method within one of my controllers, and the code looks like this:
public HttpResponseMessage Put(int idAssessment, int idCaseStudy, string value)
{
var response = Request.CreateResponse();
if (!response.Headers.Contains("Content-Type"))
response.Headers.Add("Content-Type", "text/plain");
response.StatusCode = HttpStatusCode.OK;
return response;
}
When I PUT to that location with the browser via AJAX, it gives me this Exception:
Misused header name. Make sure request headers are used with HttpRequestMessage, response headers with HttpResponseMessage, and content headers with HttpContent objects.
But isn't Content-Type a perfectly valid header for a response? Why am I getting this exception?
Have a look at the HttpContentHeaders.ContentType Property:
response.Content.Headers.ContentType = new MediaTypeHeaderValue("text/plain");
if (response.Content == null)
{
response.Content = new StringContent("");
// The media type for the StringContent created defaults to text/plain.
}
Something is missing in ASP Web API: the EmptyContent type. It will allow sending an empty body while still allowing all content-specific headers.
Put the following class somewhere in your code :
public class EmptyContent : HttpContent
{
protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
{
return Task.CompletedTask;
}
protected override bool TryComputeLength(out long length)
{
length = 0L;
return true;
}
}
Then use it as you wish. You now have a content object for your extra headers.
response.Content = new EmptyContent();
response.Content.Headers.LastModified = file.DateUpdatedUtc;
Why use EmptyContent instead of new StringContent(string.Empty)?
StringContent is a heavy class that executes lots of codes (because it inherits ByteArrayContent) so let's save a few nanoseconds
so let's save a few nanoseconds
StringContent will add an extra useless/problematic header: Content-Type: plain/text; charset=... so let's save a few network bytes
so let's save a few network bytes
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.Contentis null)? I'm wanting to set the Content-Type header even though there's no content, otherwise Firefox complains with a "no element found" error.response.StatusCode = HttpStatusCode.NoContentinstead of adding the Content-Type header field.response.Content = new StringContent("");worked. I am still left wondering whyresponse.Headerseven exists, though.Content-related.