How create a Remote Test set using version5 API

Hi 

Am trying to create remote test set using soap service version 5 

am getting nullable exception while calling

var testSet = new RemoteTestSet() { Name = name, TestSetStatusId = 1, TestSetFolderId = parentFolderId,IsAutoScheduled = false,IsDynamic = false};

 testSet = soapServiceClientTestSet_Create(testSet); and passing custom properties using integer value of custom fileds

exception details : 

   at System.Nullable`1.get_Value()
   at Inflectra.SpiraTest.Web.Services.v5_0.SoapService.TestSet_Create(RemoteTestSet remoteTestSet)
   at SyncInvokeTestSet_Create(Object , Object[] , Object[] )
   at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
   at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc)
   at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)

please suggest me to how create remote test set

programming language :C#