I am a new at depth of the Entity Framework I have just wondered why Entity Framework doesn't save changes especially the navigation property although all other properties are already updated Please I want simple explanation
This is My Service Class
public class ProductsService
{
AppDbContext _Context;
public ProductsService()
{
_Context = new AppDbContext();
}
public Product GetProduct(int id)
{
return _Context.Products.Include(p=>p.Category).Where(pro =>pro.Id == id).SingleOrDefault();
}
public void UpdateProduct(Product product)
{
_Context.Entry(product).State = System.Data.Entity.EntityState.Modified;
_Context.SaveChanges();
}
}
In Controller:
[HttpPost]
public ActionResult Edit(NewCategoryViewModel pro,int Id)
{
CategoriesService ser = new CategoriesService();
var NewProduct = ProService.GetProduct(Id);
var NewCat = ser.GetCategory(pro.CategoryId);
NewProduct.Description = pro.Description;
NewProduct.Name = pro.Name;
NewProduct.Price = pro.Price;
NewProduct.Category = NewCat;
ProService.UpdateCategory(NewProduct);
return RedirectToAction("ProductTable");
}
I have tried this and it works fine
[HttpPost]
public ActionResult Edit(NewCategoryViewModel pro,int Id)
{
using (var Context = new AppDbContext())
{
var NewProd = Context.Products.FirstOrDefault(pr => pr.Id == Id);
var Cat = Context.Categories.FirstOrDefault(cat => cat.Id == pro.CategoryId);
Context.Entry(NewProd).State = EntityState.Modified;
NewProd.Name = pro.Name;
NewProd.Description = pro.Description;
NewProd.Price = pro.Price;
NewProd.Category = Cat;
Context.SaveChanges();
}
}
and for UpdateCategory
public void UpdateCategory(Category category)
{
using (var Context = new AppDbContext())
{
Context.Entry(category).State = System.Data.Entity.EntityState.Modified;
Context.SaveChanges();
}
}
Why the first one Not work I know may be the problem in the state of the navigation property
Since you created the DbContext
inside ProductService
and you created a new Context inside:
public void UpdateCategory(Category category)
{
using (var Context = new AppDbContext())
{
Context.Entry(category).State = System.Data.Entity.EntityState.Modified;
Context.SaveChanges();
}
}
-> you use two different DbContext
's together (which can cause problems with change tracking)!
Solution:
Try to use DependencyInjection for all DbContext
's instead of creating them locally to prevent problems with change tracking.
You might consider using .add() instead of .entry(). .add() will also track other reachable entities.
documentation can be found here: entity framework