How to group Northwind orders based on Customer ContactName

Question

I am new to C# and LINQ and I am using Northwind database. My view displays all orders from the database without ordering. I want to display orders based on contact name (customer) and alphabetically: for example, AVARIA and under it all orders of this customer. And so on...

I want something like this:

AVARIA

ORDER 1 OF AVARIA FROM DATABASE WITH ITS DETAILS 
ORDER 2 OF AVARIA FROM DATABASE WITH ITS DETAILS  
ORDER 3 OF AVARIA FROM DATABASE WITH ITS DETAILS  

BECUA

ORDER 1 OF BECUA FROM DATABASE WITH ITS DETAILS
ORDER 2 OF BECUA FROM DATABASE WITH ITS DETAILS  

and so on... 

Because this is showing me all the orders coming from the database without any ordering, like customer X in the first row with an order, then customer Y, then again customer X with another order, and so on. I tried this:

public ActionResult Index()
{
    var orders = db.Orders.Include(o => o.Customer).Include(o => o.Employee).Include(o => o.Shipper);
    var list = orders.OrderBy(x => x.Customer.ContactName);

    return View(list.ToList());
}

But it raised the following exception:

An exception of type 'System.Data.Entity.Core.EntityCommandExecutionException' occurred in EntityFramework.SqlServer.dll but was not handled in user code

The view works fine.

Please help.

Answer 1

you can use group by and orderby. sample:

class Program
{

    class grpitem
    {
        public string groupCode;
        public string item;
    }

    static List<grpitem> list = new List<grpitem>()
    {
         new grpitem() {groupCode="3", item="b"},
         new grpitem() {groupCode="1", item="b"},
         new grpitem() {groupCode="3", item="c"},
         new grpitem() {groupCode="2", item="b"},
         new grpitem() {groupCode="2", item="a"},
         new grpitem() {groupCode="2", item="c"},
         new grpitem() {groupCode="1", item="a"},
         new grpitem() {groupCode="3", item="a"},
         new grpitem() {groupCode="3", item="d"}
    };

    static void Main(string[] args)
    {
        IEnumerable<grpitem> ordered = list.GroupBy(grp => grp.groupCode)
            .SelectMany(g => g.OrderBy(grp => grp.item)).OrderBy(g => g.groupCode);

        foreach(grpitem g in ordered)
            Console.WriteLine("groupCode:{0} item:{1}",g.groupCode,g.item);

        Console.ReadLine();
    }
}

Output:

groupCode:1 item:a
groupCode:1 item:b
groupCode:1 item:c
groupCode:1 item:d
groupCode:2 item:a
groupCode:2 item:b
groupCode:3 item:a
groupCode:3 item:b
groupCode:3 item:c