ReadAsMultipartAsync引发System.ArgumentException

Question

我试过在这里搜索和谷歌寻找答案但尚未找到答案。我使用我发现的相当标准的.NET 4.0上传到Web API服务。这是代码：

    public HttpResponseMessage Post()
    {
        if (!Request.Content.IsMimeMultipartContent())
        {
            throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
        }
        StringBuilder sb = new StringBuilder();

        string root = HttpContext.Current.Server.MapPath("~/App_Data");
        var provider = new MyMultipartFormDataStreamProvider(root);

        var task = Request.Content.ReadAsMultipartAsync(provider).ContinueWith<HttpResponseMessage>(t =>
        {
            if (t.IsFaulted || t.IsCanceled)
            {
                Request.CreateErrorResponse(HttpStatusCode.InternalServerError, t.Exception);
            }

            // This will give me the form field data
            foreach (var key in provider.FormData.AllKeys)
            {
                foreach (var val in provider.FormData.GetValues(key))
                {
                    sb.Append(string.Format("{0}: {1}", key, val));
                }
            }

            // This will give me any file upload data
            foreach (MultipartFileData file in provider.FileData)
            {
                sb.Append(file.Headers.ContentDisposition.FileName);
                sb.Append("Server file path: " + file.LocalFileName);
            }
            return new HttpResponseMessage()
            {
                Content = new StringContent(sb.ToString())
            };
        });
        return Request.CreateResponse(HttpStatusCode.OK);
    }

当我使用input type = file创建一个非常基本的表单并提交它时，我会收到超过800Kb的文件的异常抛出。这是一个例外：

System.ArgumentException was unhandled by user code
  HResult=-2147024809
  Message=Value does not fall within the expected range.
  Source=mscorlib
  StackTrace:
       at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)
       at System.Runtime.InteropServices.Marshal.ThrowExceptionForHR(Int32 errorCode)
       at System.Web.Hosting.IIS7WorkerRequest.GetServerVariableInternal(String name)
       at System.Web.Hosting.IIS7WorkerRequest.GetServerVariable(String name)
       at System.Web.Hosting.IIS7WorkerRequest.GetRemoteAddress()
       at System.Web.HttpWorkerRequest.IsLocal()
       at System.Web.Configuration.CustomErrorsSection.CustomErrorsEnabled(HttpRequest request)
       at System.Web.HttpContextWrapper.get_IsCustomErrorEnabled()
       at System.Web.Http.WebHost.HttpControllerHandler.<>c__DisplayClassa.<ConvertRequest>b__9()
       at System.Lazy`1.CreateValue()
       at System.Lazy`1.LazyInitValue()
       at System.Lazy`1.get_Value()
       at System.Web.Http.HttpConfiguration.ShouldIncludeErrorDetail(HttpRequestMessage request)
       at System.Net.Http.HttpRequestMessageExtensions.CreateErrorResponse(HttpRequestMessage request, HttpStatusCode statusCode, Func`2 errorCreator)
       at System.Net.Http.HttpRequestMessageExtensions.CreateErrorResponse(HttpRequestMessage request, HttpStatusCode statusCode, Exception exception)
       at aocform.Controllers.ValuesController.<>c__DisplayClass2.<Post>b__1(Task`1 t) in c:\Users\fred_malone\Documents\Visual Studio 2012\Projects\aocform\aocform\Controllers\ValuesController.cs:line 30
       at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()
       at System.Threading.Tasks.Task.Execute()
  InnerException: 

我检查App_Data文件夹，然后在那里看到部分文件。这个小部件也不总是相同的尺寸，例如它可能会切断一定的尺寸。

我已将maxRequestLength和maxAllowedContentLength调整为大数，但没有成功。

这条消息意味着什么，我应该注意什么来修复它？

感谢。