I have a Partial View that has the contains this snippet of BeginUmbracoForm:

@model ProductFilterModel
@using (@Html.BeginForm("Search", "ProductSearch", new {model = new ProductFilterModel(),@Model.YearId, @Model.MakeId, @Model.ModelId, Engine = @Model.EngineId }, FormMethod.Get, new { @class = "vehicle-filter group", @id = "productFilterForm" }))
{...

When the Search Action is called, the model object is null, but the other values are fine. I was trying to just pass model = new ProductFilter(MakeId = @Model.MakeId....), but it is null when it hits the Action. Here is the Action method:

//model is null, but the other string values are not
public ActionResult Search(ProductFilterModel model, string yearId, string makeId, string modelId, string engineId)
        {

            var db = new Database("productsDb");
            var productSearchResultsModel = new ProductSearchResultsModel
            {
                ProductFilterModel = new ProductFilterModel{ YearId = yearId, MakeId = makeId, ModelId = modelId, EngineId = engineId},
                Products = db.Fetch<ProductViewModel>(@"SELECT DISTINCT(p.ProductID) As ProductId, Type, Name, PartNumber, ShortDescription
                                                        FROM Products p
                                                        INNER JOIN productlink pl on pl.ProductID = p.ProductID
                                                        INNER JOIN vehicles v on v.VehicleID = pl.VehicleID
                                                        WHERE Brand = 'SCT'
                                                        AND v.Make = @MakeId
                                                        AND v.Model = @ModelId
                                                        AND v.Engine = @EngineId
                                                        AND v.Year = @YearId", new { YearId = yearId,MakeId = makeId,ModelId = modelId,EngineId = engineId  })
            };

            return View("~/Views/Filter.cshtml",productSearchResultsModel);
        }