StatusCode in HttpRequestException

[vanillajonathan]

When the EnsureSuccessStatusCode method in the HttpResponseMessage throws a HttpRequestException exception it is not possible to determine the status code.

Add a new property named StatusCode to the HttpRequestException class which gets set by the EnsureSuccessStatusCode method of the HttpResponseMessage class.

Rationale and Usage

Allows you to determine the status code which triggered the exception.

try
{
    DoSomeHttp();
}
catch (HttpRequestException e)
{
    Log($"Request failed with status code: {e.StatusCode}.");
}

private void DoSomeHttp()
{
    // ...
    message.EnsureSuccessStatusCode();
}

Proposed API

public class HttpRequestException : Exception
{
    // ...
    public HttpRequestException(string message, StatusCode statusCode);
    public HttpRequestException(string message, Exception inner, StatusCode statusCode);
    // ...
    public StatusCode StatusCode { get; }
    // ...
}

Open Questions

Should the property have a setter?
Should the exception have a constructor that sets the property?
Should the property be nullable?

[davidsh]

HttpRequestException is only thrown when an HTTP response can't be obtained from the server. I.e. the server is down or other errors. So, there is no HTTP status code received at all since there is no HTTP response ever sent on the wire.

This is unlike the older HttpWebRequest API which will throw WebException for non-successful status code returns (i.e. not 2xx). That API has a WebResponse in the WebException if the exception is being caused due to non 2xx status code. For other errors, there is no WebResponse in the WebException.

So, I'm not sure the goal of your request to add a StatusCode to the HttpRequestException. Can you please clarify?

[davidsh]

cc: @stephentoub

[vanillajonathan]

@davidsh HttpRequestException is thrown by the EnsureSuccessStatusCode method in the HttpResponseMessage class when IsSuccessStatusCode is false.

https://github.com/dotnet/corefx/blob/6b5ef121ebea45b14f489a177e2e3f27fce86781/src/System.Net.Http/src/System/Net/Http/HttpResponseMessage.cs#L148-L165

[davidsh]

@davidsh HttpRequestException is thrown by the EnsureSuccessStatusCode method in the HttpResponseMessage class when IsSuccessStatusCode is false.

Yes, that is true. However, I don't quite see the value in adding a StatusCode property to the HttpRequestException. In most cases, this property will be null. In fact, it would have to be a nullable property since 0 can't be used since it could (in theory) be a status code.

What is the scenario where you need this property on the HttpRequestException object?

[vanillajonathan]

I've only come across HttpRequestException from EnsureSuccessStatusCode when dealing with HttpClient so I didn't know that it would be null in most cases, if so then perhaps they ought to be throwing different exceptions.

In my scenario I call a method that use HttpClient and when an exception is thrown from that method then I can catch it and if I had the status code available in the exception then I could log it, display something relevant message in the user interface or handle it in meaningful way such as offering authentication options.

[Priya91]

@vanillajonathan Can you update the original issue with api-proposal?

[vanillajonathan]

@Priya91 Done. :)

[Priya91]

The property should just be a getter, otherwise the code receiving the exception can change the status code, but the other values on the exception will be invalid.

You should add a contructor that takes in status code for the exception, and expose only getter on the property..

[vanillajonathan]

@Priya91 Okay I edited the post and declared the StatusCode property as as setter-only without a getter.
I also added constructors. The class have 3 constructors. Not sure how many needs to be added, maybe 3?

[Priya91]

@vanillajonathan I just did a search for HttpRequestException in our System.Net.Http codebase, and it is infact in a lot of cases where we use this exception without a statuscode like @davidsh remarks. It is only in the case where you pointed out in code we have a statuscode, and it is given as part of the exception message. It doesn't make sense to add a StatusCode on this exception, because it is not true that every httprequestexception has a statuscode, it is not a property on the behavior of the type.

[Priya91]

For your scenario you could try catch the httprequestexception, and parse the string message for a statuscode and throw a different custom exception from your app.

[Priya91]

In most cases, this property will be null. In fact, it would have to be a nullable property since 0 can't be used since it could (in theory) be a status code.

It could be kept as -1

[davidsh]

It could be kept as -1

Sure. But adding this property doesn't seem useful when the majority of time, it will be -1.

[Priya91]

The proposed API doesn't work well in majority of the scenarios, and adding a new api for usability purposed for a particular narrow case doesn't seem worth the cost. Closing.