Unable to cast object of type 'System.Web.Mvc.ViewResult' to type 'System.Web.Mvc.PartialViewResult

Question

I have Html.Action method i my layout.cshtml file, which rander search form on every page. In the layout file I have this condition rendering:

@if (dcmodel != null)
{
    @Html.Action("SearchForm", "Document", dcmodel)
}
else
{
    @Html.Action("SearchForm", "Document")
}

In document controller I have this code:

[ChildActionOnly]
public ActionResult SearchForm()
{
    DocumentSearchModel model = (DocumentSearchModel)TempData["SearchForm"];

    var documentSearchModel = new DocumentSearchModel();

    if (model != null)
    {
        documentSearchModel = model;
    }

    AccessRight accessRight = unitOfWork.PermissionRepository.GetBOPermission(ApplicationViewRight.Document);
    documentSearchModel.ViewModelPermission = new ViewModelPermission(accessRight);

    documentSearchModel.DocumentStatuses = CreateDocumentStatusSelectList();
    documentSearchModel.DocumentTypes = CreateDocumentTypeSelectList();
    documentSearchModel.Storages = CreateStoragesSelectList();

    AccessRight documentAccessRight = unitOfWork.PermissionRepository.GetBOPermission(ApplicationViewRight.ShreddingManagement);

    documentSearchModel.IsShreddingAvailable = documentAccessRight.HasFlag(AccessRight.Create);
    documentSearchModel.IsUserSupervisor = unitOfWork.UserRepository.IsUserSupervisor();

    documentSearchModel.ShowLuceneSearch = unitOfWork.SystemSettingRepository.GetSettingsByCode("UseLuceneSearch").Value.ToLower() == "true";

    return PartialView("_SearchForm", documentSearchModel);
}

    [HttpPost]
    public ActionResult SearchForm(DocumentSearchModel searchModel)
    {

        var dataRequest = this.HttpContext.Request;

        Stream req = Request.InputStream;
        req.Seek(0, System.IO.SeekOrigin.Begin);
        string json = new StreamReader(req).ReadToEnd();

        var input = JsonConvert.DeserializeObject(json);

        TempData["SearchFormJson"] = input;

        TempData["SearchForm"] = searchModel;
        return RedirectToAction("Index");
    }

WhenI logOn to thepage everythink is working... When I change localtime +2 hours and refresh the page I got this error below.

What I´m doing wrong ? Please help! Thnaks!

Unable to cast object of type 'System.Web.Mvc.ViewResult' to type 'System.Web.Mvc.PartialViewResult

at TT.MVCClient.Controllers.DocumentController.SearchForm() in C:\Projects\TT\Controllers\DocumentController.cs:line 138 at lambda_method(Closure , ControllerBase , Object[] ) at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) 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.ControllerActionInvoker.<>c__DisplayClass13.b__10() at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)

{"Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'."}