Creating and populating an object with complex types

Question

I'm working on an API that will ultimately return a data extract in JSON format. This isn't my exact code. I've simplified the idea so I can convey my question more clearly.

There's a method that queries the database and returns the following columns: CustomerID, CustomerName, Preference, PreferenceValue (where one customer will have dozens of preferences). The dataset is ordered by CustomerID.

My goal is to return a JSON object like this:

{
  "Customer": {
    "CustomerID": "123",
    "CustomerName": "John Smith",
    "CustomerPreferences": {
      "Color": "Red",
      "Texture": "Rough",
      "Size": "Medium",
      "Weight": "Heavy"
    }
  }
}

I'm new to C# and OO. So, to these ends, I've been researching and trying various approaches all day. I can do this with a single object no problem, but not with a nested class. My intuition tells me what I'm trying to do shouldn't be much harder... but it continues to elude me.

I tried this (it didn't work). I made this class (note: it is the same shape as the JSON I'm hoping to get):

public class Customer
{
    public string CustomerID { get; set; }
    public string CustomerName { get; set; }
    public class Preferences 
    {
        public string Preference { get; set; }
        public string PreferenceValue { get; set; }
    }
}

Then I created the objects (although at this point, I'm already sure I'm on the wrong path, since I'm forced to initialize them separately):

List<Customer> lstCustomer = new List<Customer>();
List<Customer.Preference> lstPref = new List<Customer.Preference>();

Then I tried looping through my query results... (not sure why I'm still sharing this, since I know it doesn't work, and I'm likely embarrassing myself!!):

if (rdr.HasRows)
{
    string CurrentCustomer = "";
    while (rdr.Read())
    {
        /*
       Since the data is sorted by CustID, 
       I only add the parent class when it changes.
       */
        if (CurrentCustomer != rdr["CustID"].ToString())
        {
            lstCustomer.Add(new Customer
            {
                CustomerID = rdr["CustID"].ToString(),
                CustomerName = rdr["CustomerName"].ToString()
            });
            CurrentCustomer = rdr["CustID"].ToString();
        }

        lstPref.Add(new Customer.Preference
        {
            PrefName = rdr["PreferanceName"].ToString(),
            PrefValue = rdr["PreferenceValue"].ToString()
        });

    }
}

I have the feeling this is relatively easy. I've been searching and searching, and cannot find the solution. Once I have an object created and populated, returning it as JSON is a snap. But I can't figure out how to create this simple data structure!

Miniver Cheevy · Accepted Answer · 2016-12-08 21:35:53Z

You're not that far off. I'd go with something like this

public class Customer
    {
        public string CustomerID { get; set; }
        public string CustomerName { get; set; }
        public Dictionary<string, string> Preferences { get; set; }
        public Customer()
        {
            Preferences = new Dictionary<string, string>();
        }

    }

and

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

            if (rdr.HasRows)
            {
                Customer CurrentCustomer = new Customer();
                while (rdr.Read())
                {
                    /*
                   Since the data is sorted by CustID, 
                   I only add the parent class when it changes.
                   */
                    if (CurrentCustomer.CustomerID != rdr["CustID"].ToString())
                    {
                        CurrentCustomer = new Customer()
                        {
                            CustomerID = rdr["CustID"].ToString(),
                            CustomerName = rdr["CustomerName"].ToString()
                        };
                        customers.Add(CurrentCustomer);
                    }
                    CurrentCustomer.Preferences.Add(rdr["PreferanceName"].ToString(),
                         rdr["PreferenceValue"].ToString());
                }
            }

but try not to butcher the formatting like I did ...

ScoobyDrew18 · Accepted Answer · 2016-12-08 21:33:31Z

1

It seems to me your JSON structure and your class structure don't really match. Instead of a nested class, consider using a dictionary to match a preference name to its value.

public class Customer
{
    public string CustomerID { get; set; }
    public string CustomerName { get; set; }
    public Dictionary<string, string> Preferences { get; }
}

Then you can add preferences to your dictionary using the usual add method.

answered Dec 8, 2016 at 21:33

ScoobyDrew18

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Comments

AJ X. · Accepted Answer · 2016-12-08 22:33:07Z

0

Move preferences outside of your Customer class, and define a property instead:

public class Customer
{
    public string CustomerID { get; set; }
    public string CustomerName { get; set; }
    public List<Preference> Preferences { get; set;}
}

public class Preference
{
    public string Preference { get; set; }
    public string PreferenceValue { get; set; }
}

edited Dec 8, 2016 at 22:33

answered Dec 8, 2016 at 21:29

AJ X.

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