Catch External API Error Message as in Postman Body

Question

I am using the following code to complete an External API call.

  WebResponse response = request.GetResponse();

  string JSONResult = null;
  var data = response.GetResponseStream();
  using (var reader = new StreamReader(data))
  {
    JSONResult = reader.ReadToEnd();
  }

When there is an exception on the external API, the request.GetResponse throws an error. However, I cannot get the message that is displayed, e.g.

{
        "Message": "No HTTP resource was found that matches the request URI '<site>/Foo'.",
        "MessageDetail": "No type was found that matches the controller named 'Foo'."
 }

Whilst this is displayed in Fiddler and Postman, I cannot get this message anywhere when it is thrown as an exception.

How do I get this specific details when an error on an external API's call is made?

Answer 1

You need to catch the exception and then read the response stream of the exception. Reading the exception's response stream is the same as reading the response of the request. Here is how:

WebRequest request = 
WebRequest.Create("http://...");
WebResponse response = null; 
try
{
    response = request.GetResponse();
}
catch (WebException webEx)
{
    if (webEx.Response != null)
    {
        using (var errorResponse = (HttpWebResponse)webEx.Response)
        {
            using (var reader = new StreamReader(errorResponse.GetResponseStream()))
            {
                string error = reader.ReadToEnd();
                // TODO: use JSON.net to parse this string
            }
        }
    }
}

Do not put all your code inside the above try block because you are only try(ing) and catch(ing) the request.GetResponse(). The rest of your code needs to go outside that try catch block so you can catch the exceptions from that code separately.