TextFieldParser working in console app but not in Unity

Question

The following code works in a console app, but not in Unity 2020.3.2.f1

public RectTransform parent;
public RectTransform prefab;

public void Start()
{
    Setup();
}

public void Setup()
{
    StartCoroutine(Rolling());
}

public IEnumerator Rolling()
{
    string path = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "\\n.txt";
    Dictionary<string, Medal> medals = LoadMedals(path);

    foreach (KeyValuePair<string, Medal> entry in medals)
    {
        RectTransform medal = (RectTransform)Instantiate(prefab, parent);
        medal.name = entry.Key;
        medal.GetComponent<MedalDisplayer>().medal = entry.Value;
        medal.GetComponent<MedalDisplayer>().Setup();

        yield return null;
    }
}

public Dictionary<string, Medal> LoadMedals(string csvFile)
{
    Dictionary<string, Medal> returnDict = new Dictionary<string, Medal>();
    string[] delimiters = new string[] { "," };

    using (TextFieldParser parser = new TextFieldParser(csvFile))
    {
        parser.Delimiters = delimiters;
        parser.TextFieldType = FieldType.Delimited;
        parser.HasFieldsEnclosedInQuotes = true;

        string[] split = null;

        while (!parser.EndOfData)
        {
            split = parser.ReadFields();
            returnDict.Add(split[0], new Medal(split[0], split[1], split[2], split[3], split[4], split[5], split[6], split[7], split[8]));
        }
    }

    return returnDict;
}

Why is that?

I've added the Microsoft.VisualBasic.dll to my unity project in a Assets / Plugins folder and I've checked the reference dependencies in the C# script. All should be fine.

My console output after running in Unity:

NullReferenceException: Object reference not set to an instance of an object

MedalManager.LoadMedals (System.String csvFile) (at Assets/MedalManager.cs:42)
MedalManager+d__4.MoveNext () (at Assets/MedalManager.cs:21)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <10564ed154d647e194bef4aef8878649>:0)
UnityEngine.MonoBehaviour:StartCoroutine(IEnumerator)
MedalManager:Setup() (at Assets/MedalManager.cs:16)
MedalManager:Start() (at Assets/MedalManager.cs:12)