ASP.NET MVC | DropDownListFor给出错误的对象引用未设置为对象的实例

Question

i want to have a dropdown in my view.

but that dropdown should have categories loaded from database.

I am using Entity Framework Code First Approach in MVC 5.

Here is My

Model.

public class CreateProductModel
{

        [Required]
        public string Name { get; set; }

        [Required]
        public int CategoryID { get; set; }
        public SelectList Categories { get; set; } 

        [MaxLength]
        public double Price { get; set; }

        public string Description { get; set; }


}

Controller:

public ActionResult Index()
{
    var model = new ProductModel();
    model.CreateProductModel.Categories = new SelectList(_db.Categories, "CategoryID", "Name", 1);
    return View(model);
}

View:

                <div class="form-group">
                    @Html.LabelFor(model => model.CreateProductModel.CategoryID, new { @class = "col-lg-2 control-label" })
                    <div class="col-lg-10">
                        @Html.DropDownListFor(model => model.CreateProductModel.CategoryID, new SelectList(Model.CreateProductModel.Categories, "CategoryID", "Name", 1), "Please Select Category");
                    </div>
                </div>

I am getting this error..

Answer 1

Initialize CreateProductModel property:

var model = new ProductModel();
model.CreateProductModel = new CreateProductModel();
model.CreateProductModel.Categories = new SelectList(_db.Categories, "CategoryID", "Name", 1);