CorsMiddleware.cs

using Microsoft.AspNetCore.Http;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;

namespace MEU.API.MiddleWare
{
    public class CorsMiddleware
    {
        private readonly RequestDelegate _next;

        public CorsMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task Invoke(HttpContext context)
        {
            context.Response.Headers.Add("Access-Control-Allow-Origin", "*");
            context.Response.Headers.Add("Access-Control-Allow-Credentials", "true");
            // Added "Accept-Encoding" to this list
            context.Response.Headers.Add("Access-Control-Allow-Headers", "Content-Type, X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Accept-Encoding, Content-Length, Content-MD5, Date, X-Api-Version, X-File-Name");
            context.Response.Headers.Add("Access-Control-Allow-Methods", "POST,GET,PUT,PATCH,DELETE,OPTIONS");
            // New Code Starts here
            if (context.Request.Method == "OPTIONS")
            {
                context.Response.StatusCode = (int)HttpStatusCode.OK;
                await context.Response.WriteAsync(string.Empty);
            }
            // New Code Ends here

            await _next(context);
        }
    }
}