Dotnet Core Web Api Authendication in C#

using System;

using System.Net.Http.Headers;

using System.Security.Claims;

using System.Text;

using System.Text.Encodings.Web;

using System.Threading.Tasks;

using Microsoft.AspNetCore.Authentication;

using Microsoft.AspNetCore.Http;

using Microsoft.Extensions.Logging;

using Microsoft.Extensions.Options;

namespace MovejobtoWms.Helpers

{

    public class CustomAuthenticationHandler : AuthenticationHandler<AuthenticationSchemeOptions>

    {

        // private readonly IUserService _userService;

        public CustomAuthenticationHandler(

            IOptionsMonitor<AuthenticationSchemeOptions> options,

            ILoggerFactory logger,

            UrlEncoder encoder,

            ISystemClock clock)

            : base(options, logger, encoder, clock)

        {

            //_userService = userService;

        }

        protected override async Task<AuthenticateResult> HandleAuthenticateAsync()

        {

            if (!Request.Headers.ContainsKey("Authorization") || !Request.Headers.ContainsKey(""))

            {

                return AuthenticateResult.Fail("Missing Authorization Header");

            }

            // User user = null;

            try

            {

                var authHeader = AuthenticationHeaderValue.Parse(Request.Headers[""]);

                var tokenkey = AuthenticationHeaderValue.Parse(Request.Headers[""]);

                var credentialBytes = Convert.FromBase64String(authHeader.Parameter);

                var credentials = Encoding.UTF8.GetString(credentialBytes).Split(new[] { ':' }, 2);

                var username = credentials[0];

                var password = credentials[1];

                // user = await _userService.Authenticate(username, password);

                bool isvalid = tokenkey.Scheme.Equals("");

                bool isvalidusrNamePassword = username.Equals("") && password.Equals("");

                if (isvalid && isvalidusrNamePassword)

                {

                    var claims = new[] {

                new Claim(ClaimTypes.NameIdentifier,System.Environment.UserName),

                new Claim(ClaimTypes.Name, System.Environment.UserName),

            };

                    var identity = new ClaimsIdentity(claims, Scheme.Name);

                    var principal = new ClaimsPrincipal(identity);

                    var ticket = new AuthenticationTicket(principal, Scheme.Name);

                    return AuthenticateResult.Success(ticket);

                }

                else if (isvalid && !isvalidusrNamePassword)

                {

                    return AuthenticateResult.Fail("Invalid UserName and Password");

                }

                else if (!isvalid && !isvalidusrNamePassword)

                {

                    return AuthenticateResult.Fail("Invalid Token Key");

                }

                else

                {

                    return AuthenticateResult.Fail("Both Token key and UserName Password Incorrect");

                }

               

            }

            catch

            {

                return AuthenticateResult.Fail("Invalid Authorization Header");

            }

        }

    }

}