Populating mvc4 viewmodel with multiple List<>

Question

I have a list of 22 categories with about 8 menuItems per category, but my viewmodel ends up with only the last item in the list. I'm having a hard time seeing where the problem is.
At this point I'm sure the problem is in how I'm populating the viewmodel but I don't know where the problem is.

The ViewModels:

public class MenuViewModel    

    public List<CategoryViewModel> CategoryList { get; set; }

public class CategoryViewModel
{
    public int CategoryID { get; set; }
    public string CategoryTitle { get; set; }
    public List<MenuItemViewModel> MenuItemList { get; set; }
}

public class MenuItemViewModel
{
    public string Title { get; set; }
    public string Note { get; set; }
    public string Description { get; set; }
    public List<PriceViewModel> PriceList { get; set; }

}

public class PriceViewModel
{
    public decimal PriceValueRegularLunch { get; set; }
    public decimal PriceValueSmallLunch { get; set; }
    public decimal PriceValueLargeLunch { get; set; }

    public decimal PriceValueRegularDinner { get; set; }
    public decimal PriceValueSmallDinner { get; set; }
    public decimal PriceValueLargeDinner { get; set; }

    public decimal PriceValueRegularTakeOut { get; set; }
    public decimal PriceValueSmallTakeOut { get; set; }
    public decimal PriceValueLargeTakeOut { get; set; }
}

private MenuViewModel LoadViewModel(int menuNameID)        
{

        List<Category> returnedCategories = GetAllMenuDataModel.GetAllMenuItemsByCategory(menuNameID);

        MenuViewModel vmMenu = new MenuViewModel();

        PriceViewModel vmPrices = new PriceViewModel();

        foreach (Category category in returnedCategories)
        {
            CategoryViewModel vmCategory = new CategoryViewModel
                                               {
                                                   CategoryID = category.categoryId,
                                                   CategoryTitle = category.categoryTitle
                                               };

            foreach (MenuItem menuItem in category.MenuItems)
            {
                MenuItemViewModel vmMenuItem = new MenuItemViewModel
                                                   {
                                                       Title = menuItem.itemTitle,
                                                       Description = menuItem.itemDescription,
                                                       Note = menuItem.itemNote
                                                   };

                foreach (Price price in menuItem.Prices)
                {
                    switch (price.MealType.mealName.ToLower())
                    {
                        case "lunch":
                            if (price.ServingSize.sizeName == "Regular")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            if (price.ServingSize.sizeName == "Small")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            if (price.ServingSize.sizeName == "Large")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            break;
                        case "dinner":
                            if (price.ServingSize.sizeName == "Regular")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            if (price.ServingSize.sizeName == "Small")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            if (price.ServingSize.sizeName == "Large")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            break;
                        case "takeOut":
                            if (price.ServingSize.sizeName == "Regular")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            if (price.ServingSize.sizeName == "Small")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            if (price.ServingSize.sizeName == "Large")
                            {
                                vmPrices.PriceValueLargeLunch = price.priceValue;
                            }
                            break;
                    }

                    vmMenuItem.PriceList = new List<PriceViewModel> { vmPrices };
                }

                vmCategory.MenuItemList = new List<MenuItemViewModel> { vmMenuItem };
            }
            vmMenu.CategoryList = new List<CategoryViewModel> { vmCategory };
        }
        return vmMenu;
    }

score 2 · Accepted Answer · answered Jan 11 '13 at 15:13

Yes, the problem is with the way you are populating your view model. You must initialize the lists and then add items to them:

private MenuViewModel LoadViewModel(int menuNameID)
{
    List<Category> returnedCategories = GetAllMenuDataModel.GetAllMenuItemsByCategory(menuNameID);
    MenuViewModel vmMenu = new MenuViewModel();
    vmMenu.CategoryList = new List<CategoryViewModel>();
    foreach (Category category in returnedCategories)
    {
        CategoryViewModel vmCategory = new CategoryViewModel
        {
            CategoryID = category.categoryId,
            CategoryTitle = category.categoryTitle
        };
        vmCategory.MenuItemList = new List<MenuItemViewModel>();

        foreach (MenuItem menuItem in category.MenuItems)
        {
            MenuItemViewModel vmMenuItem = new MenuItemViewModel
            {
                Title = menuItem.itemTitle,
                Description = menuItem.itemDescription,
                Note = menuItem.itemNote
            };
            vmMenuItem.PriceList = new List<PriceViewModel>();

            foreach (Price price in menuItem.Prices)
            {
                PriceViewModel vmPrices = new PriceViewModel();
                switch (price.MealType.mealName.ToLower())
                {
                    case "lunch":
                        if (price.ServingSize.sizeName == "Regular")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        if (price.ServingSize.sizeName == "Small")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        if (price.ServingSize.sizeName == "Large")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        break;
                    case "dinner":
                        if (price.ServingSize.sizeName == "Regular")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        if (price.ServingSize.sizeName == "Small")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        if (price.ServingSize.sizeName == "Large")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        break;
                    case "takeOut":
                        if (price.ServingSize.sizeName == "Regular")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        if (price.ServingSize.sizeName == "Small")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        if (price.ServingSize.sizeName == "Large")
                        {
                            vmPrices.PriceValueLargeLunch = price.priceValue;
                        }
                        break;
                }
                vmMenuItem.PriceList.Add(vmPrices);
            }
            vmCategory.MenuItemList.Add(vmMenuItem);
        }
        vmMenu.CategoryList.Add(vmCategory);
    }
    return vmMenu;
}

score 1 · Answer 2 · answered Jan 11 '13 at 15:10

1

This would be because at the bottom of the loop, instead of adding items to the list, you're creating a new list with one item in it.

vmMenuItem.PriceList.Add(vmPrices) (and the same for vmCategory and vmMenu) would solve this problem.

answered Jan 11 '13 at 15:10

Remy Porter

353
1
3
12

sorry, I'm not sure how to change it. – NNassar Jan 11 '13 at 15:13
Oh I see. Okay I did this as well but I'll get the nullReference error on the ".PriceList" – NNassar Jan 11 '13 at 15:15
that's because you didn't initialised the lists first; have a look at my answer :) – Adam Bilinski Jan 11 '13 at 15:16

score 0 · Answer 3 · answered Jan 11 '13 at 15:13

0

Add this at the top

 vmMenuItem.PriceList = new List<PriceViewModel> ;
    vmCategory.MenuItemList = new List<MenuItemViewModel> ;
    vmMenu.CategoryList = new List<CategoryViewModel> ;

and then at the end do

                  vmMenuItem.PriceList.Add(vmPrices );
                }
                vmCategory.MenuItemList.Add(vmMenuItem);
            }
            vmMenu.CategoryList.Add(vmCategory );

You were not adding you were replacing them with new ones

answered Jan 11 '13 at 15:13

Adam Bilinski

1,188
1
18
28

the reason why this will not work is because if I put those things at the top "vmCategory" and "vmMenuItem" have not been introduced in the code yet so they will not be recognized. Thank you for having an input. – NNassar Jan 11 '13 at 15:33

Populating mvc4 viewmodel with multiple List<>

3 Answers3