vb.net code not working.


This vb.net code not working. What is problem. Please help me.

Sub Main()
    Using server As New DnsServer(10, 10)
        AddHandler server.QueryReceived, AddressOf OnQueryReceived

        Console.WriteLine("Press any key to stop server")
    End Using
End Sub

Private Function OnQueryReceived(sender As Object, e As QueryReceivedEventArgs) As Task

        Dim query As DnsMessage = TryCast(e.Query, DnsMessage)

        If query Is Nothing Then
            Return Nothing
        End If

        Dim response As DnsMessage = query.CreateResponseInstance()

        ' check for valid query

        If (query.Questions.Count = 1) AndAlso (query.Questions(0).RecordType = RecordType.Any) AndAlso (query.Questions(0).Name.Equals(DomainName.Parse("altinsoft.com"))) Then

            response.ReturnCode = ReturnCode.NoError

            response.AnswerRecords.Add(New ARecord(DomainName.Parse("altinsoft.com"), 3600, IPAddress.Parse("")))

            response.ReturnCode = ReturnCode.NxDomain
        End If

        ' set the response
        e.Response = response

 End Function

Error Message :

DNS_Server_test.vshost.exe Error: 0 : Exception in DnsServer: System.ArgumentException: Tasks argument contained a null value.

Parameter name: tasks
location: System.Threading.Tasks.Task.WhenAll(IEnumerable1 tasks)
location: ARSoft.Tools.Net.AsyncEventHandlerExtensions.RaiseAsync[T](AsyncEventHandler
1 eventHandler, Object sender, T eventArgs)
location: ARSoft.Tools.Net.Dns.DnsServer.<ProcessMessageAsync>d__22.MoveNext()
--- Starting position before the end of the stack trace where the exception was created ---
location: System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
location: System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
location: System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
location: ARSoft.Tools.Net.Dns.DnsServer.<HandleUdpListenerAsync>d__24.MoveNext()