Exception not caught when thrown by RESTSharp

Question

I'm using RestSharp to communicate with a REST-Server and wrote a small wrapper function for the call

private T Get<T>(string restAdress) where T : new()
{
    try
    {
        // throw new Exception(); // This one is caught
        IRestClient restClient = new RestClient(settings.Value.HostToConnect).UseSerializer(new JsonNetSerializer()); // (1)
        RestRequest restRequest = new RestRequest(restAdress);
        IRestResponse<T> result = restClient.Get<T>(restRequest); // (2)
        return result.Data;
    }
    catch (Exception e) // debugger wont stop here
    {
        // debugger wont stop here too
        // code within this block is not executed
    }

    return null; // (3)
}

Since I want to use the Newtonsoft-Attributes I give in a custom (de)serializer (1).

    public class JsonNetSerializer : IRestSerializer
    {
        public string Serialize(object obj) =>
            JsonConvert.SerializeObject(obj);

        public string Serialize(RestSharp.Parameter bodyParameter) =>
            JsonConvert.SerializeObject(bodyParameter.Value);

        public T Deserialize<T>(IRestResponse response) =>
            JsonConvert.DeserializeObject<T>(response.Content); // (4)

        public string[] SupportedContentTypes { get; } =
        {
            "application/json", "text/json", "text/x-json", "text/javascript", "*+json"
        };

        public string ContentType { get; set; } = "application/json";

        public DataFormat DataFormat { get; } = DataFormat.Json;
    }

When calling the REST service and trying to get the result (2) an Exception is thrown if the deserialization fails (4). But the Exception is not caught by the try-catch block. I tried to debug but after throwing the debugger goes on in line (3), the catch and the logging withing the catch is never executed. The debugger won't even stop at the catch (Exception e) it goes straight from (4) to (3).

(Sorry for not english, the title of the window says "Exception User-Unhandled")

Can anyone explain this behaviour to me?

Answer 1

I am maintaining RestSharp, so I hope I can answer this.

RestSharp doesn't throw on deserialisation by default. If you look at the code, deserialisation happens in the private IRestResponse<T> Deserialize<T>(IRestRequest request, IRestResponse raw) method of RestClient .

When RestSharp can't deserialise the response, it creates an error response. You get the response status set to Error and the exception is put into the ErrorException property of the response object, along with the exception message that gets to the ErrorMessage of the response.

It is still possible to tell RestSharp to throw on deserialisation if you assign the FailOnDeserialization property of the RestClient instance to true .

Answer 2

Whats happening here is an interesting setting of the debugger, another example would be this closed bug report . When the debugger reaches the point the exception is thrown it will break, causing the behaviour you experienced.

If you uncheck the exception setting "Break when this exception type is user-unhandled" in the dialog, you should be able to reach your catch block, as the debugger no longer breaks the execution as soon as the specified exception is thrown.

In your case you find that option under "Ausnahmeeinstellungen".