c# - 数据未在循环中保存在 ModelList 变量中。 "Index was out of range"

Question

我知道这是一个常见问题，但我找不到原因。

模型 1:

public class BsSingleCategoryProductModel
    {
        public BsSingleCategoryProductModel()
        {
            Products = new List<ProductOverviewModel>();
        }
        public int Id { get; set; }
        public string Name { get; set; }
        public string SeName { get; set; }
        public IList<ProductOverviewModel> Products { get; set; }
    }

模型 2:

public class BsMultipleCategoryProductModel
    {

        public BsMultipleCategoryProductModel()
        {
            
            SubCategories = new List<Category>();
            SubCategoriesProduct = new List<BsSingleCategoryProductModel>();
        }
        public int Id { get; set; }
        public string Name { get; set; }
        public string SeName { get; set; }
        public IList<Category> SubCategories { get; set; }
        public IList<BsSingleCategoryProductModel> SubCategoriesProduct { get; set; }
    }

这是我的 Controller Utility Meyhod(不是 Action):

public string ReturnProductsByCategoryId(int categoryId)
        {
            
            
            var subcategories = _categoryService.GetAllCategoriesByParentCategoryId(categoryId, true).ToList();

            
 
            if (subcategories.Count > 0)
            {
                var category = _categoryService.GetCategoryById(categoryId);
                var model = new BsMultipleCategoryProductModel();
                model.SubCategories = subcategories;
                model.Id = category.Id;
                model.Name = category.Name;
                model.SeName = category.GetSeName();
                
                int i = 0;
                foreach (var subcategory in subcategories)
                {
                    model.SubCategoriesProduct[i] = PrepareProductsInCategory(subcategory.Id);
                    i++;
                }
                

                return RenderPartialViewToString("AllProductsInCategoryWithSubcategory", PrepareProductsInCategory(categoryId));

            }else
            {
                return RenderPartialViewToString("AllProductsInCategory", PrepareProductsInCategory(categoryId));
            }
          
        }

这是另一种方法:

public BsSingleCategoryProductModel PrepareProductsInCategory(int categoryId)
        {
            var model = new BsSingleCategoryProductModel();
            var category = _categoryService.GetCategoryById(categoryId);
            var categoryIds = new List<int>();
            categoryIds.Add(categoryId);
            IPagedList<Product> products = new PagedList<Product>(new List<Product>(), 0, 1);
            products = _productService.SearchProducts(categoryIds: categoryIds,
                                                    storeId: _storeContext.CurrentStore.Id,
                                                   visibleIndividuallyOnly: true);

            
            model.Id = category.Id;
            model.Name = category.Name;
            model.SeName = category.GetSeName();
            model.Products = PrepareProductOverviewModels(products).ToList();

            return model;
        }

在 ReturnProductsByCategoryId 方法的 foreach 循环中 model.SubCategoriesProduct[i] 出现该错误。

索引超出范围。必须为非负且小于集合大小。参数名称:index

我进行了调试，值生成正确。每当值试图插入 model.SubCategoriesProduct[i] 时，它会在循环的第一次显示该错误。如何解决？有任何想法吗？提前致谢。

Answer 1

这个

SubCategoriesProduct = new List<BsSingleCategoryProductModel>()

创建一个长度为 0 的列表。这意味着 SubCategoriesProduct[i] 将对任何 i 失败，因为它试图访问没有元素的列表的元素。

对于您的情况，您可以改为执行 Add:

model.SubCategoriesProduct.Add(PrepareProductsInCategory(subcategory.Id));