Databasanslutningar till olika databaser i ASP.Net Core

services.AddSingleton<IDbConnection, MySqlConnection>();

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http.Headers;
using System.Text;
using API.Db.Interfaces;
using API.Helpers;
using Dapper;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace API.Db
{
    public class MySqlConnection : ControllerBase, IDbConnection
    {
        private readonly IHttpContextAccessor _context;

        public MySqlConnection(IHttpContextAccessor context)
        {
            _context = context;

            if (context.HttpContext == null) throw new Exception("No content...");

            SimpleCRUD.SetDialect(SimpleCRUD.Dialect.MySQL);
        }

        public T Get<T>(int id)
        {
            using System.Data.IDbConnection connection = new MySql.Data.MySqlClient.MySqlConnection(ConnectionString());
            return connection.Get<T>(id);
        }

        private string ConnectionString()
        {
            var apiUser = GetApiUser(_context.HttpContext?.Request.Headers);
            return $"Server={apiUser.DbHost};Database={apiUser.DbDatabase};Uid={apiUser.DbUser};Pwd={apiUser.DbPwd};Port={apiUser.DbPort}";
        }

        private static ApiUserModel GetApiUser(IHeaderDictionary headers)
        {
            var authHeader = AuthenticationHeaderValue.Parse(headers["Authorization"]);
            var credentialsByes = Convert.FromBase64String(authHeader.Parameter ?? string.Empty);
            var credentials = Encoding.UTF8.GetString(credentialsByes).Split(':');
            var username = credentials[0];
            var password = credentials[1];

            using System.Data.IDbConnection connection = new MySql.Data.MySqlClient.MySqlConnection("Server=db.exempel.se;Port=3306;Database=ApiAccounts;Uid=användarnamn;Pwd=lösenord;");

            var user = connection.Query<ApiUserModel>("SELECT * FROM users WHERE username = @Username AND password = @Password;",
                new
                {
                    Username = username,
                    Password = password
                }).SingleOrDefault();

            return user;
        }
    }
}