How to upload Genesys Purecloud CSV ContactList

ContactListService.cs

using System;
using System.IO;
using System.Net.Http;
using System.Text.Json;
using System.Threading.Tasks;

namespace PCUploadContactList
{
    public class ContactListService
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="fileToUpload">CSV file</param>        
        /// <param name="contactListId">Purecloud ContactListId</param>
        /// <param name="accessToken">Purecloud AccessToken</param>
        /// <returns></returns>
        public static async Task<ContactListUploadResponse> UploadAsync(FileDetailsProvider fileToUpload, string contactListId, string accessToken)
        {
            var api = "https://apps.mypurecloud.ie/uploads/v2/contactlist";
            try
            {
                var byteContent = fileToUpload.ReadBytes();

                using (var client = new HttpClient())
                {
                    var form = new MultipartFormDataContent();
                    client.DefaultRequestHeaders.Add("authorization", $"bearer {accessToken}");
                    form.Add(new StringContent(contactListId), "id");
                    form.Add(new StringContent("contactlist"), "fileType");
                    //very important to use same column as in Purecloud ContactList.
                    form.Add(new StringContent("FULL PHONE"), "contact-id-name");
                    form.Add(new ByteArrayContent(byteContent, 0, byteContent.Length), "file", Path.GetFileName(fileToUpload.Name));
                    var response = await client.PostAsync(api, form);
                    response.EnsureSuccessStatusCode();

                    var responseResult = await response.Content.ReadAsStringAsync();
                    return JsonSerializer.Deserialize<ContactListUploadResponse>(responseResult);                    
                }
            }
            catch (System.Exception ex)
            {
                return new ContactListUploadResponse
                {
                    Exception = ex
                };
            }            
        }
    }

    public class ContactListUploadResponse
    {
        public string CorelationId { get; set; }
        public Exception Exception { get; set; }
    }

    public class FileDetailsProvider
    {
        private readonly string _filePath;
        public FileDetailsProvider(string filePath)
        {
            _filePath = filePath;
        }
        public byte[] ReadBytes() => File.ReadAllBytes(_filePath);
        public string Name => Path.GetFileName(_filePath);
    }

}

How to upload csv js example.
How to create contactlists API documentation.

IMPORTANT contact-id-name should be one of the columnNames. After csv upload Purecloud will create contact record with unique Id based on contact-id-name.

POST ContactList body request example

{
    "name": "<contact list name>",
    "division": {
        "id": "<divisions Id>,
        "name": "<divisions name>",
        "homeDivision": true
    },
    "phoneColumns": [
        {
            "columnName": "Phone",
            "type": "Cell"
        }
    ],
    "columnNames": [
        "Phone",
        "FULL PHONE",
        "Name"
    ],
    "previewModeColumnName": "Name",
    "previewModeAcceptedValues": [
        "client1",
        "client2",
        "client3"
    ],
    "attemptLimits": null,
    "automaticTimeZoneMapping": false,
    "zipCodeColumnName": null
}

How to add contacts to ContactList API documentation.