ASP.NET MVC Web API : Posting a list of objects

Question

I'm trying to post a list of objects from my winforms application to my asp.net mvc 4 website. I've tested posting one object, and it works, but does not work for the list. It returns a 500 (Internal Server Error). Here is my code:

ASP.NET MVC Web API

public class PostTraceController : ApiController
{
    public HttpResponseMessage Post(List<WebTrace> list)
    {
        try
        {
            // Some code
            return Request.CreateResponse(HttpStatusCode.Created);
        }
        catch (Exception ex)
        {
            HttpContext.Current.Trace.Write("exception", ex.Message);
            return Request.CreateErrorResponse(HttpStatusCode.ServiceUnavailable, ex);
        }
    }

    public HttpResponseMessage Post(WebTrace item)
    {
        try
        {
            // Some code
            return Request.CreateResponse(HttpStatusCode.Created);
        }
        catch (Exception ex)
        {
            HttpContext.Current.Trace.Write("exception", ex.Message);
            return Request.CreateErrorResponse(HttpStatusCode.ServiceUnavailable, ex);
        }
    }
}

Win forms application

public class BaseSender
{
    public BaseSender()
    {
        Client = new HttpClient
        {
            BaseAddress = new Uri(@"http://localhost/mywebsite/")
        };

        Client.DefaultRequestHeaders.Accept.Add(
            new MediaTypeWithQualityHeaderValue("application/json"));
    }

    public string UserCode { get; set; }
    protected readonly HttpClient Client;

    public HttpResponseMessage PostAsJsonAsync(string requestUri, object value)
    {
        var response = Client.PostAsJsonAsync(requestUri, value).Result;
        response.EnsureSuccessStatusCode();
        return response;
    }
}

public class WebTraceSender : BaseSender
{
    private const string requestUri = "api/posttrace";

    public bool Post(List<ArchiveCptTrace> list)
    {
        try
        {
            var listWebTrace = new List<WebTrace>();
            foreach (var item in list)
            {
                listWebTrace.Add(new WebTrace
                    {
                        DateStart = item.DatePreparation,
                        DateEnd = item.DateCloture,
                        UserStart = item.UserPreparation.UserName,
                        UserEnd = item.UserCloture.UserName,
                        AmountStart = item.MontantPreparation,
                        AmountEnd = item.MontantCloture,
                        TheoricAmountEnd = item.MontantTheorique,
                        Difference = item.Ecart,
                        UserCode = UserCode
                    });
            }

            var responce = PostAsJsonAsync(requestUri, listWebTrace);
            return responce.IsSuccessStatusCode;
        }
        catch (Exception e)
        {
            // TODO : Trace the exception
            return false;
        }
    }
}

EDIT :

I've found out the scenario of the error, which is having two methods in my api controller, even thought they have different signature. If I comment one method, the post work fine (item or a list). Any ideas ?

Do you see an error message in the 500 response. if so, could you share what it is? — Kiran
– Kiran, Commented Jan 18, 2014 at 18:13
@KiranChalla : No, unfortunately no message, even in the trace page (localhost/mywebsite/trace.axd) — SidAhmed
– SidAhmed, Commented Jan 19, 2014 at 7:06

Greg Ennis · Accepted Answer · 2014-01-19 12:18:00Z

2

The methods may have different signatures, but Web API can't tell the difference between them without inspecting the body, which it won't do for performance reasons.

You could do two things - either create a new class which just holds a list of WebTrace objects, and put that in a different API controller, or you could map a custom route to one of your existing methods. You could do that with ActionName attribute, however, I would probably take the first approach.

answered Jan 19, 2014 at 12:18

Greg Ennis

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2 Comments

SidAhmed Over a year ago

+1 For the explanation, and your response was more than helpful. Although the first approach seems to be seductive, I've choosen to go with the routing approach for a maintenability reason, and more specificaly, Attribute Routing (asp.net/web-api/overview/web-api-routing-and-actions/…). Thanks again :-)

Greg Ennis Over a year ago

Yes attribute routing is the way to go now, not ActionName attribute. thanks I will update the answer

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