connectionString is not considered

Hello everyone,

I'm still in a phase of preparing a website and I am creating the first tables with Entity Framework 6. I'm developing with Visual Stuido 2015 Community in ASP.NET MVC core upgraded to .Net 1.1 Core. The problem origined when I tried to run the command "dotnet ef migrations add FirstMigrations" which continues to report me "Value cannot be null.Parameter name: connectionString", but in reality it is inside both "applicationsettings.json" that the "webconfig".

Only when in the instruction "services.AddDbContext <ApplicationIdentityDbContext> (options => options.UseSqlServer ("Server = servername; Database = databasename; Trusted_Connection = True; MultipleActiveResultSets = true "));" I explicitly set the connection string to the command has been successful. Instead with the statement: "services.AddDbContext <ApplicationIdentityDbContext> (options => options .UseSqlServer (config.GetConnectionString (" connectionString "))) this fails. Below the code of the following files:

1.  appsettings.json

{"Logging": {"IncludeScopes": false,"LogLevel": {"Default": "Debug","System": "Information","Microsoft": "Information"

    }

  },


"ConnectionStrings": {"connectionStringName": ["Server=servername; Database=databasename; Trusted_Connection=True;","MultipleActiveResultSets=true"]

  }

}

2. Web.config

<?xml version="1.0" encoding="utf-8"?><configuration><!--
    Configure your application settings in appsettings.json. Learn more at http://go.microsoft.com/fwlink/?LinkId=786380
  --><system.webServer><handlers><add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified"/></handlers><!--<aspNetCore processPath="%LAUNCHER_PATH%" arguments="%LAUNCHER_ARGS%" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" forwardWindowsAuthToken="false"/>
    --></system.webServer><connectionStrings><add name="connectionStringName" connectionString="Server=servername;Database=databasename;Integrated Security=true;MultipleActiveResultSets=true" /></connectionStrings></configuration>

3. Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.EntityFrameworkCore;
using WebCSI.Models;

namespace WebCSI
{
    public class Startup
    {
        public IConfigurationRoot config;
        //public IConfigurationRoot Configuration { get; }

        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();
            config = builder.Build();
        }

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

            services.AddDbContext<ApplicationIdentityDbContext>(options => options
                            .UseSqlServer("Server=servername; Database=databasename; Trusted_Connection=True;MultipleActiveResultSets=true"));
            //  .UseSqlServer(config.GetConnectionString("connectionStringName")));
            services.AddIdentity<ApplicationUser, ApplicationRole>()
                            .AddEntityFrameworkStores<ApplicationIdentityDbContext>()
                            .AddDefaultTokenProviders();

            // Add framework services.
            services.AddMvc();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(config.GetSection("Logging"));
            loggerFactory.AddDebug();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseBrowserLink();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            app.UseStaticFiles();
            // Inserito per la gestione delle Identity
            app.UseIdentity();
            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }
}

Regards,

Paolo