Unable to check null for header value in request

Question

I tried to get header value like below -

IEnumerable<string> headerValues = request.Headers.GetValues("MyCustomerId");
var id = headerValues.FirstOrDefault();

If header value is null or not present it is throwing error - InvalidOperationException

The null check for GetValues doesn't serve any value as it will never return null. If the header doesn't exist you will get an InvalidOperationException

Any trick to do so?

Try catch is not a good option it will break my code i need to use it in if else — Neo, Feb 17 '16 at 09:36
You can either use the `?` or check if `.Headers.HasKeys()` returns true. — Jevgeni Geurtsen, Feb 17 '16 at 09:38
Possible duplicate http://stackoverflow.com/questions/3530041/getting-a-request-headers-value ? — Pikoh, Feb 17 '16 at 09:39

Oluwafemi · Accepted Answer · 2016-02-17T10:25:47.063

5

You can check for null like so:

 if(System.Web.HttpContext.Current.Request.Headers["MyCustomerId"] != null)
   {
      // do something
   }

Tried and tested

edited Feb 17 '16 at 10:25

answered Feb 17 '16 at 09:39

Oluwafemi

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the name `Request` does not exist in current context – Neo Feb 17 '16 at 10:21

score 4 · Answer 2 · answered Feb 17 '16 at 09:39

4

request.Headers is an instance of System.Net.Http.HttpHeaders (via the HttpRequestHeaders subclass). It has a method TryGetValues which can be used to safely retrieve the values of a header.

String header = null;
IEnumerable<String> headerValues;
if( this.Request.Headers.TryGetValues("HeaderName", out headerValues) ) {
    header = headerValues.First();
}

answered Feb 17 '16 at 09:39

Dai

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the name `Request` does not exist in current context – Neo Feb 17 '16 at 10:21
@Neo where is your code getting the `request` variable from? My code assumes it's in an instance method of an `ApiController` subclass. – Dai Feb 17 '16 at 17:33
Request variable.from.requestmessage ...ur.code.also.works.fine.thanks – Neo Feb 17 '16 at 17:38
HttpHeaders also has a Contains test. – Paul Kienitz May 15 '18 at 20:06

score 3 · Answer 3 · answered Nov 27 '18 at 14:54

3

You can use Headers.Contains() to test the existence of any headers.
See examples in this answer.

answered Nov 27 '18 at 14:54

Jpsy

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Unable to check null for header value in request

3 Answers3