Entity Framework Code First Linq MVC 3 Razor

Question

This is my model;

namespace AtAClick.Models
{
    public class LocalBusiness
    {
        public int ID { get; set; }

        public string Name { get; set; }
        public int CategoryID { get; set; }
        public string address { get; set; }
        public string desc { get; set; }
        public int phone { get; set; }
        public int mobile { get; set; }
        public string URL { get; set; }
        public string email { get; set; }
        public string facebook { get; set; }
        public string twitter { get; set; }

        public string ImageUrl { get; set; }

        public virtual Category Category { get; set; }

    }

    public class Category
    {
        public int CategoryID { get; set; }
        public string Name { get; set; }

        public virtual ICollection<LocalBusiness> Businesses { get; set; }
    }

}

I have a view which lists the categories and one which lists the businesses. I want another which list all the business in a certain category My question is, what would my Linq query in my controller look like? Something like..

var companyquery = from c in db.LocalBusiness
                   where c.Category = Category.Name
                   select c;

But obvioulsy this isn't working. I'm new to all this so thanks in advance for the help, and if you need anymore detail just ask. Thanks!!

My controller, is this what you mean?

 public ViewResult Browse(int id)
 {

            int categoryID = id;

            var companyquery = from c in db.LocalBusinesses
                               where c.Category.CategoryID == categoryID
                               select c;

            return View(companyquery);
 }

Peanutbag · Accepted Answer · 2011-07-13 11:38:09Z

1

You're comparing a category object (c.Category) with a static field of the Category class (Category.Name). The static field does not exist and therefor this will not compile.

You should have a variable stating the specific category object, or at least an identifier (like the CategoryID). Name is not enough, since this property is not unique (it's possible to have two different categories with the same name).

So, let's say you obtain a specific CategoryID somehow, then your LINQ query would look like:

    // The category ID to filter.
    int categoryID = 42;

    // Retrieve all companies that are listed under the given category.
    var companyquery = from c in db.LocalBusiness
                       where c.Category.CategoryID = categoryID
                       select c;

Your categoryID could, for instance, be obtained from a query parameter (declare as a controller method parameter).

answered Jul 13, 2011 at 11:38

Peanutbag

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2 Comments

Dan Over a year ago

Hi, thanks for your reply, I'm gpoing to add my controller toi my question. Is it what you mean? Thanks again!

Peanutbag Over a year ago

Yea, something like that :-) you miss a using statement to declare and initialize your objectcontext (variable called db in this case). If you call your method parameter categoryID, you can use it instantly and your URL makes more sense to the enduser (somewebsite/companies/browse/categoryID/42).

Joakim · Accepted Answer · 2011-07-13 11:23:58Z

0

Since Category has a collection of Businesses you can do

IEnumerable<LocalBusiness> result = null;
var category = db.Category.SingleOrDefault(cat => cat.Name == "an cat");
if(category != null){
    result = category.Businesses;
}

return result;

answered Jul 13, 2011 at 11:23

Joakim

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3 Comments

Dan Over a year ago

Thanks fro your reply. I get and 'Object reference not set to an instance of an object' error when I try that though.

Joakim Over a year ago

@Dan is it the category or the collection of LocalBusinesses that is "not an instance"? chances are that if it is the collection that the category found doesn't have any businesses added.

Dan Over a year ago

The error come at the start of the foreach in my view, so that's the collection of businesses. The categorey definitely has two businesses added to it. I have a view which list them.

Eranga · Accepted Answer · 2011-07-13 11:28:31Z

0

If you are filtering by category name

string categoryName = "foo";

var companyquery = from c in db.LocalBusiness
                   where c.Category.Name == categoryName
                   select c;

If you are filtering by category id

int categoryId = 1;

var companyquery = from c in db.LocalBusiness
                   where c.CategoryID == categoryId 
                   select c;

answered Jul 13, 2011 at 11:28

Eranga

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1 Comment

Dan Over a year ago

Thanks Eranga! I need the category ID to be taken in and not directly coded into the controller.

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