C# ASP.NET Middleware Code to Authenticate Telegram initData

TelegramAuthMiddleware.cs

using Microsoft.Extensions.Primitives;
using System.Security.Cryptography;
using System.Text;
using System.Web;
using System.Text.Json;
using System.Net;
using Telegram.Bot.Types;

namespace AnimalTrackz.API.Middleware
{
    public class TelegramAuthMiddleware
    {
        private readonly RequestDelegate _next;
        private const string TokenKey = "WebAppData";
        private readonly byte[]? _secretHmac;
        private readonly string _webHookSecretToken;

        public TelegramAuthMiddleware(RequestDelegate next, string botToken, string webHookSecretToken)
        {
            _next = next;

            using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(TokenKey));
            _secretHmac = hmac.ComputeHash(Encoding.UTF8.GetBytes(botToken));
            _webHookSecretToken = webHookSecretToken;
        }

        public async Task InvokeAsync(HttpContext context)
        {            
            // Webhook
            if (context.Request.Headers.TryGetValue("X-Telegram-Bot-Api-Secret-Token", out var sentBotApiSecretToken))
            {
                if (sentBotApiSecretToken != _webHookSecretToken)
                {
                    context.Response.StatusCode = ((int)HttpStatusCode.Unauthorized);
                    return;
                }
            }
            else if (context.Request.Headers.TryGetValue("X-Telegram-Bot-InitData", out var initData)) // Website inside Telegram
            {
                try
                {
                    if (StringValues.IsNullOrEmpty(initData))
                    {
                        context.Response.StatusCode = ((int)HttpStatusCode.Unauthorized);
                        return;
                    }

                    var queryStringData = HttpUtility.ParseQueryString(initData.ToString());

                    var dictData = new SortedDictionary<string, string>(
#pragma warning disable CS8714 // The type cannot be used as type parameter in the generic type or method. Nullability of type argument doesn't match 'notnull' constraint.
                        queryStringData.AllKeys.ToDictionary(key => key, key => queryStringData[key])!
#pragma warning restore CS8714 // The type cannot be used as type parameter in the generic type or method. Nullability of type argument doesn't match 'notnull' constraint.
                    );

                    var telegramAuthDateTimeOffset = DateTimeOffset.FromUnixTimeSeconds(Convert.ToInt64(dictData["auth_date"]));

                    // auth_date too old check
                    if (DateTime.UtcNow.Subtract(telegramAuthDateTimeOffset.UtcDateTime).TotalMinutes > 60)
                    {
                        context.Response.StatusCode = ((int)HttpStatusCode.RequestTimeout);
                        return;
                    }

                    /*if (!ValidateTelegramHash(dictData))
                    {
                        context.Response.StatusCode = ((int)HttpStatusCode.Unauthorized);
                        return;
                    }*/

                    var telegramUser = JsonSerializer.Deserialize<User>(dictData["user"]);
                    
                    context.Items.Add("TelegramUser", telegramUser);
                    context.Items.Add("TelegramChatInstance", dictData["chat_instance"]);
                    context.Items.Add("TelegramChatType", dictData["chat_type"]);                    
                }
                catch
                {
                    context.Response.StatusCode = ((int)HttpStatusCode.Unauthorized);
                    return;
                }
            }
            else
            {
                context.Response.StatusCode = ((int)HttpStatusCode.Unauthorized);
                return;
            }

            await _next(context);
        }

        private bool ValidateTelegramHash1(IDictionary<string, string> telegramFields)
        {
            var hash = telegramFields["hash"];
            telegramFields.Remove("hash");

            var dataStringBuilder = new StringBuilder();
            foreach (var field in telegramFields.Where(field => !string.IsNullOrEmpty(field.Value)))
            {
                dataStringBuilder.Append(field.Key);
                dataStringBuilder.Append('=');
                dataStringBuilder.Append(field.Value);
                dataStringBuilder.Append('\n');
            }
            dataStringBuilder.Remove(dataStringBuilder.Length - 1, 1);

            using var hmacData = new HMACSHA256(_secretHmac!);

            var signature = hmacData.ComputeHash(Encoding.UTF8.GetBytes(dataStringBuilder.ToString()));

            var hmacDataHex = Convert.ToHexString(signature).ToLower();

            return hmacDataHex == hash;
        }
    }
}