CSV to Dictionary - All credit to Sloane Kelly

CardClass.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Card
{

    public int CardID { get; set; }
    public int CardLvl { get; set; }
    public bool CardPlayed { get; set; }
    public string CardText { get; set; }

    public Card(int cardID, int cardLvl, bool cardPlayed, string cardText)
    {
        CardID = cardID;
        CardLvl = cardLvl;
        CardPlayed = cardPlayed;
        CardText = cardText;
    }

    public Card()
    {
        CardID = 0;
        CardLvl = 0;
        CardPlayed = false;
        CardText = "";

    }
}

DeckBuilder.cs

using System.Collections.Generic;
using System.IO;
using UnityEngine;
using System.Linq;
using LINQtoCSV;

public class DeckBuilder : MonoBehaviour
{
    private Dictionary<int, Card> CompleteDeck = new Dictionary<int, Card>();

    [Tooltip("The file that contains the list to be converted to cards. Must be in Resources folder")]
    public TextAsset CardList;

    private void CreateDeck()
    {
        CompleteDeck.Clear();

        CsvFileDescription inputFileDescription = new CsvFileDescription
        {
            SeparatorChar = ',',
            FirstLineHasColumnNames = true
        };

        using (MemoryStream ms = new MemoryStream())
        {
            using (StreamWriter txtWriter = new StreamWriter(ms))
            {
                using (StreamReader txtReader = new StreamReader(ms))
                {
                    txtWriter.Write(CardList.text);
                    txtWriter.Flush();
                    ms.Seek(0, SeekOrigin.Begin);
                    CsvContext cc = new CsvContext();
                    cc.Read<Card>(txtReader, inputFileDescription)
                        .ToList()
                        .ForEach(card =>
                        {

                            CompleteDeck[card.CardID] = new Card
                            {
                                CardLvl = card.CardLvl,
                                CardPlayed = card.CardPlayed,
                                CardText = card.CardText,
                            };
                        });

                }
            }
        }
        //(Text, P1, P1Gender, P2, P2Gender, P3, P3Gender, P4, P4Gender);
        string output = string.Format((CompleteDeck[2].CardText), "a", "b");
        Debug.Log(output);
    }


    public Dictionary<int, Card> ReturnLevelDeck(int level)
    {
        CreateDeck();

        Debug.Log(CompleteDeck.Count);
        Dictionary<int, Card> returnDictionary = new Dictionary<int, Card>();
        for (int i = 0; i < CompleteDeck.Count; i++)
            if (CompleteDeck[i].CardLvl == level)
            {
                Debug.Log("found");
                returnDictionary[CompleteDeck[i].CardID] = CompleteDeck[i];
            }
        return returnDictionary;
    }
}

GameController.cs

using System.Collections.Generic;
using UnityEngine;

public class GameController : MonoBehaviour
{
    public DeckBuilder Deck;

    public void QuitGame()
    {
        Application.Quit();
    }

    private void Awake()
    {
        TestStart();
    }

    public void TestStart()
    {
        //string output = string.Format((Deck.CompleteDeck[2].CardText), "a", "b");
        Dictionary<int, Card> Level0Cards = Deck.ReturnLevelDeck(0);
        
        //I appreciate that this doesn't make any proper use of the IEnumerable nature of the dictionary, but I wanted to see what was going on..
        for (int i = 0; i < Level0Cards.Count; i++)
        {
            string retstring = string.Format((Level0Cards[i].CardText), "James", "Bob");
            Debug.Log(retstring);
        }
    }

    //TEST CODE ONLY DOWN HERE
}

List.csv