ปรึกษาเรื่องการเชื่อมต้อ MySQL ของ .net core หน่อยค่ะ

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.UI;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using ERPWeb.Data;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using System.IO;

namespace ERPWeb
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
            var testVar0 = configuration.GetSection("DatabaseSettings")["RDBMSType"];
            var testVar1 = configuration.GetSection("DatabaseSettings")["RDBMSName"];
            var testVar2 = configuration.GetSection("DatabaseSettings")["RDBMSConnectionString"];
            //จะทำอะไรก็ว่ากันไป            
        }

        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.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });

            services.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(
                    Configuration.GetConnectionString("DefaultConnection")));

            services.AddDefaultIdentity<IdentityUser>()
                .AddDefaultUI(UIFramework.Bootstrap4)
                .AddEntityFrameworkStores<ApplicationDbContext>();

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseDatabaseErrorPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }
            
            app.UseHttpsRedirection();
            app.UseStaticFiles();

            //app.UseCookiePolicy();
            //app.UseAuthentication();

            //app.UseMvc(routes =>
            //{
            //    routes.MapRoute(
            //        name: "default",
            //        template: "{controller=Home}/{action=Index}/{id?}");
            //});
        }
    }
}