Object reference not set to an instance of an object.

at MFA.Consulate.WebMvcUI.Controllers.VisaController.<>c.<Index>b__21_0(PARAMETRE_ULKELER k) in C:\Agent\_work\15\s\KonsNETv2\Code\konsolosluk.gov.tr.v4\MFA.Consulate\MFA.Consulate.WebMvcUI\Controllers\VisaController.cs:line 500 at System.Linq.Enumerable.WhereListIterator`1.MoveNext() at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source) at MFA.Consulate.WebMvcUI.Controllers.VisaController.Index(String refn, Int32 bid) in C:\Agent\_work\15\s\KonsNETv2\Code\konsolosluk.gov.tr.v4\MFA.Consulate\MFA.Consulate.WebMvcUI\Controllers\VisaController.cs:line 500 at lambda_method(Closure , ControllerBase , Object[] ) at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3d() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult)