EF Core : how to Insert data releated tables - asp.net-mvc

Question

I'm new to Entity Framework Core and learning.
I have a question: I have three tables with many-to-many relations (Product, ProductCategory, Categories). Everything works fine, I can update, delete and add database.
But I couldn't add Product data to related tables. It just inserts into the Product table, but I want to add Id data to ProductCategories.
Thank you for helping me here.
This is my code:
Generic repository
public class EfCoreGenericRepository<TEntity, TContext> : IRepository<TEntity>
where TEntity : class
where TContext : DbContext, new()
{
public virtual void Create(TEntity entity)
{
using (var context = new TContext())
{
context.Set<TEntity>().Add(entity);
context.SaveChanges();
}
}
public void Delete(TEntity entity)
{
using (var context = new TContext())
{
context.Set<TEntity>().Remove(entity);
context.SaveChanges();
}
}
public List<TEntity> GetAll()
{
using (var context = new TContext())
{
return context.Set<TEntity>().ToList();
}
}
public TEntity GetById(int id)
{
using (var context = new TContext())
{
return context.Set<TEntity>().Find(id);
}
}
public virtual void Update(TEntity entity)
{
using (var context = new TContext())
{
context.Entry(entity).State = EntityState.Modified;
context.SaveChanges();
}
}
}
ProductRepository
public class EfCoreProductRepository : EfCoreGenericRepository<Product, FoodContext>, IProductRepository
{
public Product GetByIdWithCategories(int id)
{
using (var context = new FoodContext())
{
return context.Products
.Where(p => p.ProductId == id)
.Include(p => p.ProductCategories)
.ThenInclude(pc => pc.Category)
.FirstOrDefault();
}
}
public List<Product> GetProductsByCategory(string name)
{
using (var context = new FoodContext())
{
var products = context.Products.AsQueryable();
if (!string.IsNullOrEmpty(name))
{
products = products.Include(i => i.ProductCategories)
.ThenInclude(i => i.Category)
.Where(i => i.ProductCategories.Any(a => a.Category.Name.ToLower() == name.ToLower()));
}
return products.ToList();
}
}
public void Update(Product entity, int[] categoryIds)
{
using (var context = new FoodContext())
{
var product = context.Products
.Include(i => i.ProductCategories)
.FirstOrDefault(i => i.ProductId == entity.ProductId);
if (product != null)
{
product.Name = entity.Name;
product.Price = entity.Price;
product.ImageUrl = entity.ImageUrl;
product.ProductCategories = categoryIds.Select(catid => new ProductCategory() {
ProductId = entity.ProductId,
CategoryId = catid
}).ToList();
}
context.SaveChanges();
}
}
// I may override Create code here.
}
MVC Post method
[HttpPost]
public async Task<IActionResult> CreateProduct(ProductModel model, IFormFile file)
{
if (ModelState.IsValid)
{
if (file != null)
{
var extension = Path.GetExtension(file.FileName);
var randomName = string.Format($"{DateTime.Now.Ticks}{extension}");
model.ImageUrl = randomName;
var path = Path.Combine(Directory.GetCurrentDirectory(), "wwwroot\\img\\Products", randomName);
using (var stream = new FileStream(path, FileMode.Create))
{
await file.CopyToAsync(stream);
}
}
var entity = new Product()
{
Name = model.Name,
Price = model.Price,
ImageUrl = model.ImageUrl,
CategoryId = model.CategoryId
};
if (_productService.Create(entity))
{
TempData.Put("message", new AlertMessage
{
Title = $"{entity.Name} named product added successfully",
Message = $"{entity.Name} named product added successfully",
AlertType = "alert-success"
});
return RedirectToAction("ProductList");
};
TempData.Put("message", new AlertMessage
{
Title = _productService.ErrorMessage,
Message = _productService.ErrorMessage,
});
}
ViewBag.Categories = _categoryService.GetAll();
return View(model);
}
You can ask for more code if you need to see it. Thanks for now!
Edit ---> Entity Classes
Category.cs
public class Category
{
public int CategoryId { get; set; }
public string Name { get; set; }
public string ImageUrl { get; set; }
public List<ProductCategory> ProductCategories{get; set;}
}
Product.cs
public class Product
{
public int ProductId { get; set; }
public string Name { get; set; }
public double? Price { get; set; }
public bool IsApproved { get; set; }
public int? CategoryId { get; set; }
public string ImageUrl { get; set; }
public List<ProductCategory> ProductCategories{get; set;}
}
ProductCategories.cs
public class ProductCategory
{
public int CategoryId { get; set; }
public Category Category { get; set; }
public int ProductId { get; set; }
public Product Product{get; set;}
}

Answer 1

Thanks to Pirate. I solved problem. I'm new in efcore but i was aware of many to many relationship unnecessary. I had done for many products with many categories but I changed my mind later. Maybe I can use it for next codes.
public override void Create(Product entity)
{
base.Create(entity);
using (var context = new FoodContext())
{
var product = context.Products
.Where(i=>i.ProductId==entity.ProductId)
.Include(i=>i.ProductCategories).FirstOrDefault();
product.ProductCategories.Add(new ProductCategory(){
ProductId=entity.ProductId,
CategoryId=(int)entity.CategoryId
});
context.SaveChanges();
}
}
Note: I don't know how true using double using-code-block