Question

我正在使用一个类模型，其中我声明了一个相同类类型的列表。但是当我要在这个列表中赋值时，它给对象引用null异常，而我在分配给这个列表的参数中有一些值。

public class BackSplashTileGuideViewModel
{
    public int ID { get; set; }
    public Nullable<int> ProductID { get; set; }
    public string ProductDescription { get; set; }
    [Required(ErrorMessage ="Required")]
    public string Imagepath { get; set; }
    public string UpdateImagepath { get; set; }
    [Required(ErrorMessage = "Required")]
    public string[] Products { get; set; }
    public string MultipleProduct { get; set; }
    public string ProductsName { get; set; }
    public int CreatedBy { get; set; }
    public System.DateTime CreatedOn { get; set; }
    public Nullable<int> UpdatedBy { get; set; }
    public Nullable<System.DateTime> UpdatedOn { get; set; }
    public string Status { get; set; }
    public List<BackSplashTileGuideViewModel> lstBacksplashTile { get; set; }
}

 public ActionResult BacksplashTileInfo()
    {
        if (Session["BacksplashTileID"] != null)
        { 
            _websiteRepo = new WebsiteRepo();
            _adminRepo = new AdminRepo();
            string Name = "Backsplash & Wall Tile";
            int MasterDetailID = _adminRepo.GetMasterDetailIDByName(Name);
            var AllProducts = _adminRepo.GetAllProductsName().Where(x => x.ProductGroupID == MasterDetailID).ToList();

            int id = Convert.ToInt32(Session["BacksplashTileID"]);
            var BacksplashProduct = _websiteRepo.GetBacksplashTileByID(id);
            if(BacksplashProduct != null)
            {
                var products = BacksplashProduct.MultipleProduct.Split(',');
                for (int i = 0; i < products.Length; i++)
                {
                    var detail = AllProducts.Where(x => x.ID == Convert.ToInt32(products[i])).Select(y => new {y.ID ,y.ProductName,y.Descriptions }).FirstOrDefault();

                    BacksplashProduct.ProductID = detail.ID;
                    BacksplashProduct.ProductDescription = detail.Descriptions;
                    BacksplashProduct.ProductsName = detail.ProductName;
                    BacksplashProduct.lstBacksplashTile.Add(BacksplashProduct);
                }
                return View(BacksplashProduct);
            }
            else
            {
                return RedirectToAction("BacksplashTileGuide", "Home");
            }
        }
        else
        {
            return RedirectToAction("BacksplashTileGuide", "Home");
        }
    }

Answer 1

我认为这会对你有帮助。

在向其中添加内容之前，您必须将内存分配给列表。

if(BacksplashProduct != null)
{
    //YOu missed assignment here
    BacksplashProduct.lstBacksplashTile = new List<BackSplashTileGuideViewModel>(); 

    var products = BacksplashProduct.MultipleProduct.Split(',');
    for (int i = 0; i < products.Length; i++)
    {
        var detail = AllProducts.Where(x => x.ID == Convert.ToInt32(products[i])).Select(y => new {y.ID ,y.ProductName,y.Descriptions }).FirstOrDefault();

        BacksplashProduct.ProductID = detail.ID;
        BacksplashProduct.ProductDescription = detail.Descriptions;
        BacksplashProduct.ProductsName = detail.ProductName;
        BacksplashProduct.lstBacksplashTile.Add(BacksplashProduct);
    }
    return View(BacksplashProduct);
}

如何将列表分配到类模型中

1 个答案: