Error getting foreign key data on entity

I'm new in MVC2 and Entity Framework and I tried get a list of products with the respective category name, but it's returned me the error

"Object reference not set to an instance of an object."

I have a tab开发者_如何学Cle Product with a foreign key Category.

I'm using MVC2 and Entity Framework 4.0.

public class Repository 
{       
        public IQueryable<Produto> ListAllProducts()
        {
            return entities.Produtos;
        } 
}

public class AdminProdutoController : Controller  
{   

    TudoDeMassinhaRepository repository = new TudoDeMassinhaRepository();    

    public ActionResult Index()     
    {       
          var produtos = repository.ListAllProducts().ToList();
          return View(produtos);    
    }  
}

code in view where the error is generated: <%: item.CatProduto.cat_produto_nome%>

You're only selecting the products - you're not currently including the categories. This means: you'll get back your product objects, but any related objects they refer to are not loaded automatically - that's why the .CatProduto property will be NULL and thus you're getting the error.

You need to explicitly specify which additional entities you want to have loaded - something like:

public IQueryable<Produto> ListAllProductsWithCategories()
{
        return entities.Produtos.Include("CatProduto");
} 

This way, you should get back your Produto objects, and their CatProduto property should have been loaded and populated, too.

So if you change your index method to be:

public ActionResult Index()     
{       
      var produtos = repository.ListAllProductsWithCategories().ToList();
      return View(produtos);    
}  

it should work.