TokenHandler.cs

using System.Net.Http;
using System.Net;
using System.Net.Http.Headers;
using System.Threading;
using System.Threading.Tasks;
using System;
using System.Diagnostics;

namespace EBScan
{
    public class TokenHandler : DelegatingHandler
    {
        private readonly TokenService tokenService;

        public TokenHandler(TokenService tokenService) : base(new HttpClientHandler())
        {
            this.tokenService = tokenService;
        }

        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            string token = await tokenService.GetTokenAsync();
            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
            try
            {
                return await base.SendAsync(request, cancellationToken);
            }
            catch (Exception ex)
            {
                Debug.WriteLine($"TokenHandler: Exception {ex.Message}");
                return new HttpResponseMessage(HttpStatusCode.InternalServerError);
            }
        }
    }
}