title: Request Header in Angular 5.2
body: <p>I am trying to make post request. the SessionConfirmationNumber is getting removed. Everything else is fine. I can see it's value in console log</p>
  
  <pre><code>console.log('the Session Number', options.headers.sessionConfirmationNumber) //works can see the value e.g.: 23524545245
  
  return this.http
      .post(environment.domain + url, body,  { headers: new HttpHeaders({
        '_dynSessConf': options.headers.sessionConfirmationNumber,
        'Authorization_Test': 'TestValue',
        'ClientBrowserId': options.headers.clientbrowseruid,
        'Content-Type': 'application/json'
      })})
      .catch(this.config.handleError)
      .map((responseData: any) =&gt; {
        console.log('Response Data ', responseData)          
      })
  </code></pre>
  
  <p>when I check the network tab it literally removes _dynSessConf. 
  I tried hardcoding value '_dynSessConf' :'test-val'  and it works. Just when it has the value it doesnt work.
  It is very frustrating. </p>
  
  <p>I tried  creating httpHeader and appending the values </p>
  
  <pre><code>var headers = new HttpHeaders();
          headers = headers.append('Content-Type', 'application/json');
          headers = headers.append('Authorization_Test', 'TestValue');
          headers = headers.append('DynSess', options.headers.sessionConfirmationNumber);
  
      return this.http
      .post(environment.domain + url, body,  { headers: headers})
  </code></pre>
  
  <p>again i can see the values in console under lazyUpdate. But it complains about </p>
  
  <p><a href="https://i.stack.imgur.com/RoOV5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RoOV5.png" alt="enter image description here"></a></p>
  
  <pre><code>Error: Uncaught (in promise): profileService.handleProfile error TypeError: undefined is not a function
  </code></pre>