ASP.NET MVC: Getting unhandled exception that stops in a catch block of a rethrow

Question

I am seeing some strange behavior in my try/catch-rethrow code blocks.

I have a method which instantiates a class of ClientGet and gets the Result value from that class.

public Task<T> Get<T>(ClientRequest<T> Request)
    {
        try
        {
            return new ClientGet<T>(UpdateRequest(Request)).Result;
        }
        catch (Exception)
        {
            throw;
        }
    }

The ClientGet class looks like this:

public class ClientGet<T> : IClientAction<T>
{
    public Task<T> Result { get; set; }

    public ClientGet(ClientRequest<T> request)
    {
        try
        {
            Result = GetResult(request);
        }
        catch (Exception)
        {
            throw;
        }
    }

    private async Task<T> GetResult(ClientRequest<T> request)
    {
        if (string.IsNullOrEmpty(request.FullPath))
        {
            throw new ApplicationException("You must specify a path in your request.");
        }
        try
        {
            using (HttpClient client = new HttpClient())
            {
                if (!string.IsNullOrEmpty(request.Settings.Token)) { client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", request.Settings.Token); }

                var response = await client.GetAsync(request.FullPath);
                if (response.IsSuccessStatusCode)
                {
                    return JsonConvert.DeserializeObject<T>(await response.Content.ReadAsStringAsync());
                }
                throw new HttpRequestException((int)response.StatusCode + ": " + response.ReasonPhrase);
            }
        }
        catch (Exception)
        {
            throw;
        }
    }
}

If the response.IsSuccessStatusCode is false, for some reason the code stops at the catch of my GetResult method and posts it as an ASP.NET Unhandled Exception error on my throw; line. I have all of the re-throws so that the errors can be passed back up to the original caller at a higher level of the application.

Here is the exact message I get back:

401: Unauthorized Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Net.Http.HttpRequestException: 401: Unauthorized

Source Error:

Line 45:             catch (Exception)
Line 46:             {
Line 47:                 throw;
Line 48:             }
Line 49:         }

score 0 · Accepted Answer · answered Nov 20 '15 at 17:29

0

Not sure what you expect to happen. Sounds like the code is doing exactly what it should. If the condition is not satisified, it proceeds to new next line where you throw HttpRequestException, since this is all wrapped in a try-catch, that exception is caught, and then re-thrown. However, this is the first time an exception is allowed to bubble up, so this is where Visual Studio will indicate the exception originated from. It will be eventually caught by the calling method's try-catch, and then finally raised to uncaught status after it's thrown again there.

However, you're breaking a fundamental rule of using try-catch here: only catch an exception if you intend on actually handling it. If all you're going to do is throw it in the catch block, then the entire try-catch is pointless. The default behavior is to allow it to bubble up through the stack; you don't have to throw it explicitly to accomplish that.

answered Nov 20 '15 at 17:29

Chris Pratt

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Because ultimately if there is an error it is handled at one level higher than the Get method. Based on if there is an error at a lower level it is reporting back a particular page to display to the user. – Xipooo Nov 20 '15 at 17:49
That doesn't matter. If you have a try-catch around the `Get`, then you don't need *any* try-catch at any of the deeper levels, at least if all you intend to do is throw. That's my point. If an exception is generated anywhere in this code it will always bubble up, regardless of whether it was contained in a try-catch that threw it again. – Chris Pratt Nov 20 '15 at 17:55
Indeed you are correct and originally I was trying not to manually bubble it up through the stack with all of the rethrows. After further investigating I discovered I was observing the wrong caller to the method and in fact there was a missing try/catch on the originating request. Your original answer was spot on and it was behaving as it should since there was a missing catch where the error ultimately was supposed to bubble up to. – Xipooo Nov 20 '15 at 18:06

ASP.NET MVC: Getting unhandled exception that stops in a catch block of a rethrow

1 Answers1