using System;

using System.Buffers.Text;

using System.Security.Cryptography;

using System.IO;

public class Program

{

        public static void Main()

        {

            string encodedString = "eyJraWQiOiJqd2UtY2VydC0yMDIzMTIyMSIsImVuYyI6IkEyNTZHQ00iLCJhbGciOiJSU0EtT0FFUC01MTIifQ.l2w3nG3bxZDrGdPtyCETQ7TGZSvkYkS5nlTeiPWNTo9xXN4o6_FqVk6s0AoPPnWZ1NTci72grlTeqCzo-5R7BYl_0UqkcxzQ-djR86WKCyF1U0wzik_q-Pu2H6EWWTdl9DxY74bk2uvAa8VFEgCdiy570Hjjny_FSdsi9nD5iKO60FyVQpf6OBnOef7mjH_OR-D49VgwE79vFJjq42QJxm1jxaS_I86NP_CcWdBqM_NFUmCIuOvYJKFOKx_BldeLbz25p59Nf-uknKOz-TNS_BwiTgSo7goqib8t19-oh7TvIbA8keOZlCMvICrX2w0Fv0kPtScpaR7tEykNZCQEmg.4ypuloQV1hfiVuUQ.je8FWuFTMW-snap4iOh9yKL7KgU7XPEdEsVBTTpKjppJdoKGwwVYjzdghvMvuYp_89Socv4wI0zD7E0tO4YY_x-6lcegUPqUiuMIyMdQ6sAmcMJ3-GH-r8OSNCsEqCgniAM2uqz4s1svRyNgE5MHuKSBY8twBNRRCbBRosdjCcMJGQws4O2evJnhgaGENsct0W1ojcxbTkJytQDK4yeqaJiaX8-HBHQ2SBY0wGpB--_2gpqXilepiK62xmLeZInQT5BbBNOejhTufs2gsM_KkpKkF_IbOdJAlyvSNHpD0-RncjNUbuO-DbgxLVcpxUP7CHOPp2hIEMq0858M1ZHj5wUaRArl3jTNssD3cg0M8UppJqjqHYN3m7hDeiLgimRoAODxNfpZGqoye1HBBELous33fPwrdm9sTkCdy8gVoTsIMBjPAjekA0DAGT4Lnlh87my8v1Ba1O3aaBIM3Z2V5Dk59PLEbEkPE8Ym0zT4TuVZxhLKQx6YXeGiTHKeWdUSSnAyO2THSKOXcH2R2303A-hZ_cCH2QjDDjdlyu-Lkwo5QGIbfHx1fNW1sm8h5Z8u0y8aXD9NMGyqBB_xpmbQAaUszB_uXSs3aksQoARlN61VIc_vlScnXmR-EEZxBPidjgbzwXb6_Oc5Xl_O4bvDsVZTh-cilb5YExdgI61Yu_7QfqN7wdV6eGmNfnBDDX9JrnC4QPFL5_Jh.D08F210Ub3ttGO7ucxDSPw";

            FromBase64Transform transform = new FromBase64Transform();

            byte[] buffer = new byte[transform.OutputBlockSize];

            using (MemoryStream inputStream = new MemoryStream(Convert.FromBase64String(encodedString)))

            {

                using (MemoryStream outputStream = new MemoryStream())

                {

                    int inputBlockSize = transform.InputBlockSize;

                    while (true)

                    {

                        byte[] inputBytes = new byte[inputBlockSize];

                        int bytesRead = inputStream.Read(inputBytes, 0, inputBlockSize);

                        if (bytesRead == 0) break;

                        int outputBytes = transform.TransformBlock(inputBytes, 0, bytesRead, buffer, 0);

                        outputStream.Write(buffer, 0, outputBytes);

                    }

                    transform.TransformFinalBlock(buffer, 0, 0);

                    string originalString = System.Text.Encoding.UTF8.GetString(outputStream.ToArray());

                }

​

            }

            /*byte[] data = Convert.FromBase64String("stringToConvert");

            Encoding.UTF8.GetString(Convert.FromBase64String(stringToConvert));

​

            Span<byte> buffer = new byte[Base64.GetMaxDecodedFromUtf8Length(stringToConvert.Length)];

            if (Base64.TryDecodeFromUtf8(stringToConvert, buffer, out int bytesWritten))

            {

                string originalString = Encoding.UTF8.GetString(buffer.Slice(0, bytesWritten));

                Console.WriteLine(originalString); // prints "Hello World"

            }

            else

            {

                Console.WriteLine("Invalid base64 string");

            }

            string decodedString = System.Text.Encoding.UTF8.GetString(data);*/

        }

}