Joining data from two API responses-CodePudding

I am getting data from two different API calls. One gets me "customer" data, the other "towns" data. Each customer has a town reference, so in my application, I need to have the actual town object referenced by the customer object. Here is a vastly simplified representation of my classes:

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int townId { get; set; }

    public Town town { get; set; }
}

public class Town
{
    public int townId { get; set; }
    public string townName { get; set; }
}

The only way I can think of achieving my objective is as follows (assume I am actually getting the lists from my API calls, the following is just for sake of explanation of the problem):

List<Customer> customers = new List<Customer>();

customers.Add(new Customer { Id = 1, Name = "First Customer", townId = 10 });
customers.Add(new Customer { Id = 2, Name = "Second Customer", townId = 20 });
customers.Add(new Customer { Id = 2, Name = "Third Customer", townId = 20 });

List<Town> towns = new List<Town>();

towns.Add(new Town { townId = 10, townName = "Eton" });
towns. Add(new Town { townId = 20, townName = "Harrow" });
towns.Add(new Town { townId = 30, townName = "Cambridge" });

foreach(Customer c in customers)
{
    c.town = towns.Where(t => t.townId == c.townId).FirstOrDefault();
}

This does not feel like an efficient way of achieving my objective, especially when I have dozens of other places I would need to do the same sort of thing.

CodePudding user response：

As written according to your comment, you are using the original Customer object without assigning Town to the town property.

It should be:

For query expression

customers = (from a in customers
            join b in towns on a.townId equals b.townId
            select new Customer
            {
                Id = a.Id,
                Name = a.Name,
                townId = a.townId,
                town = b
            })
            .ToList();

For method expression

customers = customers
            .Join(towns,
                 x => x.townId,
                 x => x.townId,
                 (x, y) => 
                  {
                      var customer = x;
                      customer.town = y;
                      
                      return customer;
                  })
            .ToList();

CodePudding user response：

Use a join :

           var results = (from c in customers
                           join t in towns on c.townId equals t.townId
                           select new { customer = c, town = t}
                           ).GroupBy(x => x.customer.Name)
                           .ToDictionary(x => x.Key, y => y.First());

CodePudding user response：

After you are calling the 2 APIs consequently. While adding to the Customer Object.
You can do following,

customers.Add(new Customer 
             { 
                Id = cSerializedApiObj.Id, 
                Name = cSerializedApiObj.Name, 
                town =  tSerializedAPiObjList.
                         FirstorDefault
                         (x=>x.townId==cSerializedApiObj.townId)
               townId=town.townId //it isn't required anymore
             });

Now you can access the town corresponding to the customer without any joining. Also, there can be multiple ways to do this efficiently. I prefer this way. Let me know if u have any queries.