My question is this. Let's say I have a Category class and Product class. And they are implemented like this :
Category :
public class Category
{
public Category()
{
this.Products = new ObservableCollection<Product>();
}
public int CategoryId { get; set; }
public string Name { get; set; }
public virtual ObservableCollection<Product> Products { get; private set; }
}
And Product :
public class Product
{
public int ProductId { get; set; }
public string Name { get; set; }
public int CategoryId { get; set; }
public virtual Category Category { get; set; }
}
My question is this. If their id names were both "Id", how could I set the same relationship between Category and Product? In this example I can easily put CategoryId in product because the IDs have different names. What if they had the same name? What should I do? Thanks.
I think just renaming their Id(s) to "Id" work perfectly as you expected.
public class Category
{
public Category()
{
this.Products = new ObservableCollection<Product>();
}
public int Id { get; set; }
public string Name { get; set; }
public virtual ObservableCollection<Product> Products { get; private set; }
}
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public int CategoryId { get; set; }
public virtual Category Category { get; set; }
}
Result
Related
I have a list of products.
var products = await unitOfWork.ProductRepository.GetAllWithDetailsAsync();
This is the model, so far so good.
public class ProductModel
{
public int Id { get; set; }
public int ProductCategoryId { get; set; }
public string CategoryName { get; set; }
public string ProductName { get; set; }
public decimal Price { get; set; }
public ICollection<int> ReceiptDetailIds { get; set; }
}
I also have ProductCategoryModel.
public class ProductCategoryModel
{
public int Id { get; set; }
public string CategoryName { get; set; }
public ICollection<int> ProductIds { get; set; }
}
The problem is with the returned Category name. Instead of returning the correct data, it returns Data.Entities.Product.
In debug mode, after expanding product, I can expand Category and inside it is CategoryName - the expected string.
How do I show CategoryName directly instead of Category?
While requesting Products in your UnitOfWork include Category .Include("Category")
public class ProductModel
{
public int Id { get; set; }
public int ProductCategoryId { get; set; }
public string ProductName { get; set; }
public decimal Price { get; set; }
public ICollection<int> ReceiptDetailIds { get; set; }
public ProductCategoryModel Category { get; set; }
public string CategoryName => Category.CategoryName;
}
https://learn.microsoft.com/en-us/ef/ef6/querying/related-data
i have problem
i have A CategoryEntity Class :
public class Category : IId
{
[Key] public int Id { get; set; }
[Required] public string Name { get; set; }
public List<SubToCat> SubToCat { get; set; }
}
and SubCategory Entity Class :
public class SubCategory : IId
{
[Key] public int Id { get; set; }
[Required] public string Name { get; set; }
public List<SubToCat> SubToCat { get; set; }
}
and its my SubToCat entity class :
public class SubToCat
{
public int SubCategoryId { get; set; }
public int CategoryId { get; set; }
public Category Category { get; set; }
public SubCategory SubCategory { get; set; }
}
now in Get method for all SubCategory i want to join the all of categories where its CategoryId is same as CategoryId
but i dont know how, Can you plz Help me
I'm assuming you are using some Entity Framework :
_dbContext.SubCategories.Where(s => s.SubToCat.Category == CategoryId)
You do not need join. Just use SelectMany as code below :
class Program
{
static void Main(string[] args)
{
DataContext db = new DataContext();
var results = db.Category.SelectMany(x => x.SubToCat.SelectMany(y => y.SubCategory.SubToCat.Select(z => new {
catId = x.Id,
catName = x.Name,
subToSubCatId = y.SubCategoryId,
subToCatId = y.CategoryId,
subToCategory = y.Category,
subToCatSubCatId = z.SubCategory.Id,
subToCatSubCatName = z.SubCategory.Name
}).ToList():
}
}
public class DataContext
{
public List<Category> Category { get; set; }
}
public class IId
{
}
public class Category : IId
{
public int Id { get; set; }
public string Name { get; set; }
public List<SubToCat> SubToCat { get; set; }
}
public class SubCategory : IId
{
public int Id { get; set; }
public string Name { get; set; }
public List<SubToCat> SubToCat { get; set; }
}
public class SubToCat
{
public int SubCategoryId { get; set; }
public int CategoryId { get; set; }
public Category Category { get; set; }
public SubCategory SubCategory { get; set; }
}
Try
_dbContext.SubCategories
.Include(x => x.SubToCat)
.Include(x => x.Category)
This will bring in all Sub Categories as well the joining table and relevant Categories in a single SQL Query using 2 joins.
I have a question. I created a table with many to many relationships as below. What code should I write so that I can enter multiple categories when adding a product to the database?
I would be glad if you explain with an example.
For example, I can enter product.name information with the name information I received from the user, but I do not know how to save data in the relevant tables.
public class Category
{
public int CategoryId { get; set; }
public string Name { get; set; }
public string Url { get; set; }
public List<ProductCategory> ProductCategories { get; set; }
}
public class Product
{
public int ProductId { get; set; }
public string Name { get; set; }
public string Url { get; set; }
public double? Price { get; set; }
public string Description { get; set; }
public string ImageUrl { get; set; }
public bool IsApproved { get; set; }
public bool IsHome { get; set; }
public List<ProductCategory> ProductCategories { get; set; }
}
public class ProductCategory
{
public int CategoryId { get; set; }
public Category Category { get; set; }
public int ProductId { get; set; }
public Product Product { get; set; }
}
You can insert them by the join table like this:
var product = new Product { Name = "AA" };
var categories = new List<Category>
{
new Category{ Name = "a"},
new Category{ Name = "b"},
new Category{ Name = "c"},
};
foreach (var category in categories)
{
_context.ProductCategory.Add(
new ProductCategory
{
Product = product,
Category = category
});
}
_context.SaveChanges();
I am not sure which version you are using. with EF Core 5.o find an example at https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-5.0/whatsnew
Models:
public class Category
{
public int CategoryId { get; set; }
public string Name { get; set; }
public string Url { get; set; }
public ICollection<Product> Products { get; set; }
}
public class Product
{
public int ProductId { get; set; }
public string Name { get; set; }
public string Url { get; set; }
public double? Price { get; set; }
public string Description { get; set; }
public string ImageUrl { get; set; }
public bool IsApproved { get; set; }
public bool IsHome { get; set; }
public ICollection<Category> Categories { get; set; }
}
Or If you are using EE 6 or EF Core 3.1 then your models should be like:
public class Category
{
public int CategoryId { get; set; }
public string Name { get; set; }
public string Url { get; set; }
public ICollection<Product> Products { get; set; }
public ProductCategory ProductCategorie { get; set; }
}
public class Product
{
public int ProductId { get; set; }
public string Name { get; set; }
public string Url { get; set; }
public double? Price { get; set; }
public string Description { get; set; }
public string ImageUrl { get; set; }
public bool IsApproved { get; set; }
public bool IsHome { get; set; }
public ICollection<Category> Categories { get; set; }
public ProductCategory ProductCategorie { get; set; }
}
public class ProductCategory
{
public int CategoryId { get; set; }
public Category Category { get; set; }
public int ProductId { get; set; }
public Product Product { get; set; }
}
For inserting data to Many-Many tables: https://learn.microsoft.com/en-us/aspnet/core/data/ef-mvc/complex-data-model?view=aspnetcore-5.0
then please look at the section:Seed database with test data
I create an application and as an example for testing I take a table of orders. I have questions about class modeling.
I have 3 classes:
public class Car
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
}
public class Part
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
}
class Order
{
public Order()
{
Cars = new List<Car>();
Parts = new List<Part>();
}
public int OrderId { get; set; }
public int CarId { get; set; }
public int PartId { get; set; }
public ICollection<Car> Cars { get; set; }
public ICollection<Part> Parts { get; set; }
}
I do not know if this model is ok. What do you think? Because something does not go here: / In the application:
I can not add cars or parts to the order that I do not have in the database.
In the table of orders I would like to see only the order Id, the value of the order, and the Id of the car and Id of the part that was bought.
I would like the Car and Part tables to have no data about orders. I would like to only add parts or cars in the application, later only be able to select from them in the order section.
Let's start with the physical tables you will need:
Part { Id, Name, Price }
Car { Id, Name, Price }
Order { Id }
OrderPart* { OrderId, PartId }
OrderCar* { OrderId, CarId }
The last two tables are called "join tables" because you need them to be able to store multiple parts and multiple cars on the same order, but are not really tables you think of as being part of your model.
Entity Framework will automatically make these join tables if you set up your classes as follows:
public class Car
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
public virtual ICollection<Order> Orders { get; set; }
}
public class Part
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
public virtual ICollection<Order> Orders { get; set; }
}
class Order
{
public Order()
{
Cars = new List<Car>();
Parts = new List<Part>();
}
public int OrderId { get; set; }
public virtual ICollection<Car> Cars { get; set; }
public virtual ICollection<Part> Parts { get; set; }
}
Note that the ICollection<> properties on the Car and Part table will be the clue to EF that it needs to make the join table. Also, remember that you need "virtual" on your navigation properties.
It is good model ?
One Pizza may have a few idgredience
One Pizza may have one sauce under the cheese
One Order may have a few idgredience and a few sauces.
It is my classes :
public class Suace
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
public virtual ICollection<Order> Orders { get; set; }
}
public class Pizza
{
public int Id { get; set; }
public string Name { get; set; }
public double Price { get; set; }
public ICollection<Idgredient> Idgredients { get; set; }
public Sauce Sauce {get;set;}
public virtual ICollection<Order> Orders { get; set; }
}
class Order
{
public Order()
{
Cars = new List<Car>();
Parts = new List<Part>();
}
public int OrderId { get; set; }
public virtual ICollection<Car> Suace { get; set; }
public virtual ICollection<Part> Pizza { get; set; }
}
public class Idgredient
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Pizza> Pizzas { get; set; }
}
Below is a POCO class i set up with Entity Framework Code first. How can i Query my database so that I can return all brands of a specific category?
Example: You have a list of categories and you click on one. It shows all brands of products available under that category.
I don't know if my classes are set up correctly to do this.
public class Product
{
[Key,ScaffoldColumn(false)]
public int ProductID { get; set; }
public string ProductName { get; set; }
public int? CategoryID { get; set; }
public virtual Category Category { get; set; }
public int? BrandID { get; set; }
public virtual Brand Brand { get; set; }
}
public class Brand
{
[ScaffoldColumn(false)]
public int BrandID { get; set; }
public string BrandName { get; set; }
}
public class Category
{
[ScaffoldColumn(false)]
public int CategoryID { get; set; }
public string CategoryName { get; set; }
public virtual ICollection<Product> Products { get; set; }
}
What about
context.Products.
Where(p => p.Category.CategoryID == categoryToFind).Select(p => p.Brand);
or
var brands = context.Products.
Where(p => p.Category.CategoryID == categoryToFind).
Select(p => p.Brand.BrandName).Distinct().ToList();
if you just need brand names.