Question

I have a backend table as shown below and I am reading it using ado.net.

I tried to convert this to a dictionary with key value pair, but I don’t know how to map keys and values so that when I read code 1 I can return its category name, and when I read 2 as code 3 as subcode I can read both its corresponding category and subcategory?(Say ex., Old, ThreeMonth).

Is there any other type/class available to acheive this functionality?

code    Sub_Code    Category    Sub_Category
1             1     NEW                  NEW
2             1         Old             OneMonth
2             2         Old                 TwoMonth
2             3         Old                 ThreeMonth
2             4         Old                 Ninemonth
5             4     APPOINTMENT         APPOINTMENT MADE
9             4         Invalid             LANGUAGE BARRIER

Answer 1

You have a number of options, depending on what operations you need to do with the data, how often it changes, etc. Some obvious ones are:

Nested Types

Create a custom type to hold your category and its sub-categories. This has the benefit that you can skip the sub-categories if there are none, and your data type can exactly map to your business object.

public class Category 
{
  public int Id;
  public string Name;
  Dictionary<int, string> Subcategories = new Dictionary<int, string>();
}

Dictionary<int, Category> Categories;

(I’d also consider a KeyedCollection here that can extract the Id from a Category as the key directly.)

The downside: its a bit more work to add or retrieve a subcategory because you have to do two lookups:

var subcategory = Categories[1].Subcategories[1];

A 4-Tuple (quadruple?)

If your data structure rarely changes you can use a 4-field Tuple<>:

List<Tuple<int, int, string, string>> Categories;
var subcategory = Categories.Where(x => Item1 == 1 && Item2 == 1);

The biggest downside here is that it’s not indexed very well. You could alleviate that a bit, at the cost of even more complexity, by using two Tuples (one key, one value):

Dictionary<Tuple<int, int>, Tuple<string, string>> Categories;

But IMO that gets kinda messy, and at that point I’d just go with a custom class.

Split Collections

Split up the category name and subcategories into separate collections: one holds the cateogory id -> name mapping, and the other holds the category id -> subcategory mapping:

Dictionary<id, string> CategoryNames;
Dictionary<id, Dictionary<id, string>> Subcatgories;

This is more flexible than the Tuple solution but doesn’t involve a custom data type, so it’s a more “quick and dirty” solution. Also, if you commonly find yourself only caring about one or the other, having the data separate may make things more efficient.