Startup.cs

using Employee.DataAccess.Model;
using Employee.DataAccess.Repository;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.OpenApi.Models;

namespace Employee.API
{
    public class Startup
    {
        private readonly string AllowedOrigin = "allowedOrigin";

        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {

            services.AddControllers();
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "Employee.API", Version = "v1" });
            });

            services.AddDbContext<EmployeeManagementDBContext>(options =>
                options.UseNpgsql(Configuration.GetConnectionString("EmployeeManagementDBContext")));
            services.AddTransient<IEmployeeDAO, EmployeeDAO>();

            services.AddCors(option => {
                option.AddPolicy("allowedOrigin",
                    builder => builder.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader()
                    );
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseSwagger();
                app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "Employee.API v1"));
            }
            app.UseCors(AllowedOrigin);
            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}