Send info to the view from another table with navigation property? - asp.net

Question

This is my models
public class Product
{
[Key]
public int SerialNumber { get; set; }
public int PartNumber { get; set; }
public string Description { get; set; }
public virtual ICollection<Reading> Reading { get; set; }
}
public class Reading
{
[Key]
public int Id { get; set; }
public int SerialNumber { get; set; }
public int ReadingValue { get; set; }
public virtual Product Product { get; set; }
}
I can send all products to the view with
return View(db.Products.ToList().Where(product => product.CustomerID == Customer));
And I can get the latest ReadingValue if I know the Product SerialNumber
var LatestReading = db.Readings.OrderByDescending(m => m.Id).Where(s => s.SerialNumber == SerialNumber).Select(m => m.ReadingValue).FirstOrDefault();
How can I send all the products to the view with the latest ReadingValue for each product?

Answer 1

Create a new view model that will hold both the data:
public class FooViewModel
{
public List<Product> Products { get; set; }
public Reading LatestReading { get; set; }
}
Change your view to use the new model with:
#model FooViewModel
Then send them back in your controller:
var model = new FooViewModel();
model.Products = db.Products.ToList().Where(product => product.CustomerID == Customer);
model.LatestReading = db.Readings.OrderByDescending(m => m.Id).Where(s => s.SerialNumber == SerialNumber).Select(m => m.ReadingValue).FirstOrDefault();
return View(model);

Answer 2

Because you have Reading property in Products class, you can get the latest ReadingValue in the view:
foreach(Product product in Model)
{
var latestReadingValue = product.Reading.OrderByDescendin(m => m.Id).FirstOrDefault();
// do what you want here
}
but as hutchonoid points out the better option is creating a ViewModel for it, because having logic in the view is a bad practice, and it doesn't correspond to MVC pattern.