.Net Core 2 EF core connection string problem

Question

this is my appsettings.json

 "ConnectionStrings": {
    "Circolari": "Server=abcde;Database=Circolari;Trusted_Connection=True;"
  }

and this is my startup.cs

 public Startup(IConfiguration configuration, IHostingEnvironment env)
 {
        Configuration = configuration;
        IConfigurationBuilder configurationBuilder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
        Configuration = configurationBuilder.Build();
 }


 // This method gets called by the runtime. Use this method to add services to the container.

    public void ConfigureServices(IServiceCollection services)
    {
        //Circolari
        string connectoionString = Configuration.GetConnectionString("Circolari");
        services.AddDbContext<CircolariContext>(options => options.UseSqlServer(connectoionString));
        services.AddMvc();
    }

so when i do a query

using (CircolariContext db = new CircolariContext(new DbContextOptions<CircolariContext>()))
{
   List<Argomenti> listaArgomenti = db.Argomenti.ToList();
}

i have the problem: An unhandled exception occurred while processing the request.

InvalidOperationException: A named connection string was used, but the name 'Circolari' was not found in the application's configuration. Note that named connection strings are only supported when using 'IConfiguration' and a service provider, such as in a typical ASP.NET Core application. See https://go.microsoft.com/fwlink/?linkid=850912 for more information.

Microsoft.EntityFrameworkCore.Storage.Internal.NamedConnectionStringResolverBase.ResolveConnectionString(string connectionString)

could someone help me please?

Disconcerted

Are you sure your appSettings.json is being loaded? You've marked it as optional, so if env.ContentRootPath isn't the right folder, it won't be loaded. Try marking it as optional: false to see if it throws an exception. – Surrey

Your example code for "so when I do a query" does not use dependency injection, is that the actual code generating the error? I wonder how the error is getting the connection string name "Circolari" if so... – Scandent

@John i think that the configuration is loaded because if i put a breackpoint in ConfigureServices the string is readed, and with optional: false the error is still here – Disconcerted

@Scandent this is the actual code, the same i am writing in my little example for configuring ef core on .net core – Disconcerted

Use optional: false. – Humorist

var connectoionString = Configuration.GetValue<string>("ConnectionStrings:Circolari"); is another way to get from configuration – Humorist

@t-prisar if i use optional: false the problem persist – Disconcerted

@Disconcerted Is there a chance that you're loading the wrong configuration file? – Surrey

In ConfigureServices you have ˋUseSqlServer´ but in appsettings.json ˋServer=abcdé´? – Smoking

@Scandent with var connection = Configuration.GetValue<string>("ConnectionStrings:Circolari"); the problem persist – Disconcerted

@Smoking yes, the 'abcde' is a replaced string that , the correct is in appsetting.json – Disconcerted

@John i think that i am loading the correct configuration file because in 'ConfigureServices' string connectoionString = Configuration.GetConnectionString("Circolari"); give me the correction connection string – Disconcerted

Why you are using the ˋIConfigureBuider´? What version of .Net core you are using? – Smoking

@Smoking i use IConfigureBuilder because i think is the standard. Microsoft.AspNetCore.Mvc v2.1.3 Microsoft.AspNetCore v2.1.4 – Disconcerted

I think the IConfigureBuilder is used in .Net core 1.0. Check the docs for migration learn.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/… – Smoking

@Smoking now my startup is empty and i iInject IConfiguration in Startup(IConfiguration configuration) but the problem is still there – Disconcerted

But if you really are calling new CircolariContext(new DbContextOptions<CircolariContext>()), it doesn't use your configuration – Houseraising

Maybe you need to call directly without the string connectoionString – Smoking

See the Exception ˋA named connection string was used,´. – Smoking

@IvanStoev i am using this code using (CircolariContext db = new CircolariContext()) { List<Argomenti> listaArgomenti = db.Argomenti.ToList(); } – Disconcerted

@Smoking yes, but ef does not find .... and i dont know why... – Disconcerted

I think you need to call just the ˋCircularí´ connectionstring like ˋUseSqlServer(Configuration.GetConnectionString("Circolari")));´ – Smoking

@Smoking i don't want to modify this file because is generated by Scaffold-DbContext – Disconcerted

ˋstring connectoionString = Configuration.GetConnectionString("Circolari");´ is generated by Scaffold-DbContext?? – Smoking

@Llazar, no but optionsBuilder.UseSqlServer("Name=Circolari"); yes and i don't want to change code there – Disconcerted

Answer 1

YouContextFile.cs add this code

 protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
               // add IConfigurationRoot  to get connection string 
                IConfigurationRoot configuration = new ConfigurationBuilder()
                .SetBasePath(AppDomain.CurrentDomain.BaseDirectory)
                .AddJsonFile("appsettings.json")
                .Build();
                optionsBuilder.UseSqlServer(configuration.GetConnectionString("DefaultConnection"), x => x.UseNetTopologySuite());
            }
        }

Ursula

Adding this to my context has sorted my issue where I couldn't scaffold a new controller. – Lochia

Answer 2

Modify startup.cs

public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<DB_A6136B_MiGranCitaContext>(options =>
             options.UseSqlServer(Configuration.GetConnectionString("MiGranCitaDB")));

then add the controller using the option API CONTROLLER WITH ACTIONS USING ENTITY FRAMEWORK

Gladisgladney

Answer 3

Finally i found the solution to my problem:

now in asp.net core everything must be injected, so you can get yout db context via ServiceProvider (just like the compiler told me)

//this is the constructor
public EfGiacenzeRepo(IServiceProvider serviceProvider)
{
    _serviceProvider = serviceProvider;
}


//this is the method
using (_aspContext = _serviceProvider.GetService<aspContext>())
{
    listaGiacenze = _aspContext.TabGiacenza.ToList();
}

Disconcerted

Answer 4

I was seeing the same error message, and none of the solutions here solved the issue for me.

My problem was that in my DEV environment, I have multiple projects selected as startup projects.

When that is the case, it seems that Visual Studio does not know where to look for the appsettings.json file.

Temporarily switching to a single startup project solves this issue, so I do this when I need to rebuild the database models with Scaffold-DbContext.

Wristwatch