Can't set Content-Type header on HttpResponseMessage headers?

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
• StringContent will add an extra useless/problematic header: Content-Type: plain/text; charset=...
  • so let's save a few network bytes