.NET (Core and Framework)

Dim text2 As String = ""
Dim num As Integer = 1
Dim num2 As Integer
Dim num3 As Integer
Do
    ' The following expression was wrapped in a unchecked-expression
    Dim value As Integer = CInt(Math.Round(Math.Floor(CDbl((10.0F * VBMath.Rnd())))))
    text2 += Conversions.ToString(value)
    num += 1
    num2 = num
    num3 = 8
Loop While num2 <= num3

protected void GetArticleCount()
{
    ArticlesManager articlesManager = new ArticlesManager();
    ViewBag.ArticlesCount = articlesManager.ArticleCount();
}

var t1 = Task.Factory.StartNew(() => GetArticleCount());
var t2 = Task.Factory.StartNew(() => GetBrancheCount());
var t3 = Task.Factory.StartNew(() => GetCompaniesCount());
var t4 = Task.Factory.StartNew(() => GetDeliveriesCount());
var t5 = Task.Factory.StartNew(() => GetDistributionCentresCount());
var t6 = Task.Factory.StartNew(() => GetDocksCount());
var t7 = Task.Factory.StartNew(() => GetInvoicesCount());
var t8 = Task.Factory.StartNew(() => GetOrdersCount());

var taskList = new List<Task> { t1, t2, t3, t4, t5, t6, t7, t8 };
Task.WaitAll(taskList.ToArray());

Exception Details: System.FormatException: The format of value 'application/json; charset=utf-8' is invalid.

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

[FormatException: The format of value 'application/json; charset=utf-8' is invalid.]
   System.Net.Http.Headers.MediaTypeHeaderValue.CheckMediaTypeFormat(String mediaType, String parameterName) +119919
   System.Net.Http.Headers.MediaTypeHeaderValue..ctor(String mediaType) +23
   System.Net.Http.ObjectContent.BuildHeaderValue(String mediaType) +63
   System.Net.Http.ObjectContent`1..ctor(T value, MediaTypeFormatter formatter, String mediaType) +66
   System.Net.Http.HttpRequestMessageExtensions.CreateResponse(HttpRequestMessage request, HttpStatusCode statusCode, T value, HttpConfiguration configuration) +892
   System.Net.Http.HttpRequestMessageExtensions.CreateResponse(HttpRequestMessage request, HttpStatusCode statusCode, T value) +104
   System.Web.Http.Dispatcher.HttpControllerDispatcher.HandleException(HttpRequestMessage request, Exception exception, HttpConfiguration configuration) +191
   System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +284
   System.Net.Http.DelegatingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +41
   System.Web.Http.HttpServer.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +347
   System.Net.Http.HttpMessageInvoker.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +55
   System.Web.Http.WebHost.HttpControllerHandler.BeginProcessRequest(HttpContextBase httpContextBase, AsyncCallback callback, Object state) +316
   System.Web.Http.WebHost.HttpControllerHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +77
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +103
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

I searched in google but can't find the proper solution.

Please help me