Earlier today I was working on this application which requires me to make a few calls to a REST API to get some products back in XML format. In order to accomplish this task, I have instantiated an HttpClient object which to make the call. However, I was getting this security error below saying “Required OAuth credentials not provided”.

 

  900902
  Missing Credentials
  Required OAuth credentials not provided

Solution

Of course the error message is self explanatory, I was missing the authorization token in the header.

string url = "https://api.web.com/search/1.0" + ";
using (var client = new HttpClient())
{
  client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/xml"));
  client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", "my_authorization_token"); ;
  HttpResponseMessage response = client.GetAsync(new System.Uri(url)).Result;
  string responseBody = response.Content.ReadAsStringAsync().Result;
}