How do I determine what is the issue with a 500 error on a HttpClient.PostAsJsonAsync call?

Question

I am making a call to a Web API that I wrote. I am working through the bugs on both sides and am getting a 500 error. I want to see that is in that error message to see what might be the problem. How do I find that?

using (var client = new HttpClient())
{
    var fooURL = Url.RouteUrl("PayrollApi", new { httproute = string.Empty, controller = "LeaveRequest" }, Request.Url.Scheme);
    var repsonse = client.PostAsJsonAsync(fooURL, leaveRequest).Result;
}

I don't see where that text might be stored so I can figure out what other bugs need to be fixed. How do I get that text?

Update : something I didn't clarify. I put a breakpoint on the WebAPI I am calling and the break point is never hit. However , when I call it from Poster, I hit the break point. The URL is correct.

public HttpResponseMessage Post([FromBody]LeaveRequest value)
{
    if (ModelState.IsValid)
    {
        // code here
    }
}

Answer 1

I was able to make a change to get the error message:

var repsonse = client.PostAsJsonAsync(fooURL, leaveRequest).Result.Content.ReadAsStringAsync();

instead of

var repsonse = client.PostAsJsonAsync(fooURL, leaveRequest).Result;

I was then able to see my error and fix it.

Answer 2

I am making a call to a Web API that I wrote. I want to see that is in that error message to see what might be the problem.

You might want to put the code you have in PayrollApi.LeaveRequest in a try-catch block, something like:

public HttpResponseMessage LeaveRequest()
{
    try {
        // do something here
    } 
    catch(Exception ex) {
        // this try-catch block can be temporary 
        // just to catch that 500-error (or any unexpected error)
        // you would not normally have this code-block
        var badResponse = request.CreateResponse(HttpStatusCode.BadRequest);
        badResponse.ReasonPhrase = "include ex.StackTrace here just for debugging";
    }
}

Then make a call inside a try-catch block to capture that extra error:

using (var client = new HttpClient())
{
    // rest of your code goes here
    try
    {
        var repsonse = client.PostAsJsonAsync(fooURL, leaveRequest).Result;
    }
    catch(HttpRequestException httpEx)
    {
         // determine error here by inspecting httpEx.Message         
    }
}

httpEx.Message can have this message:

Response status code does not indicate success: 500 ({stack_trace_goes_here}).