If-None-Match header always null in asp.net core controller

Question

I send a request with "If-None-Match" header by postman, but it's always null in controller.

I'm using Asp.net core 1.1.

Is there anything wrong with my code?

Debug Code

if (Request.Headers.ContainsKey("If-None-Match"))
{
    var oldETag = Request.Headers["If-None-Match"].First();
    if (cache.Get($"Tenant-{id}-{oldETag}") != null)
    {
        return StatusCode((int)HttpStatusCode.NotModified);
    }
}

UPDATE 1

I create a new request with both If-Match & If-None-Match header, but only If-Match header exists in controller If-None-Match still null.

Answer 1

• You look into the wrong header in the debugger. Instead on HeaderIfMatch check HeaderIfNoneMatch

• Request.Headers.ContainsKey("If-None-Match") - this code is fine and works for me via Postman. But, accordingly to screenshot, looks like you add If-None-Match as a query parameter, not as a header.

Answer 2

Can you try this syntax? request.Headers.Keys.Contains(HeaderNames.IfNoneMatch)

You can import HeaderNames from using Microsoft.Net.Http.Headers;

Answer 3

"If-None-Match" header is removed by "CSS Hot Reload" feature. You have to disable the hot reload in the Visual Studio options if you want to see the header while debugging.