asp.net core - Value cannot be null. Parameter name: connectionString appsettings.json in starter

Question

I am trying to write my connection string in my appsettings.json file and bring it into my startup file but I keep getting a Value cannot be null. Parameter name: connectionString. I have been using various examples but can't seem to see this new setup with ASP.NET 1.0 Core startup class.

Appsetting.json file:

{
"Data": {
"DefaultConnection": {
  "ConnectionString": "Data Source=server;Initial Catalog=dbase;Trusted_Connection=True;MultipleActiveResultSets=true"

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

Method attempting Startup.cs

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();
        Configuration = builder.Build();
    }

 public void ConfigureServices(IServiceCollection services)
    {
        var connStr = Configuration.GetConnectionString("DefaultConnection");
        System.Console.WriteLine(connStr);
        services.AddDbContext<DbContext>(options => options.UseSqlServer(connStr)); //error right here -- Null value
}

question from:https://stackoverflow.com/questions/40874640/value-cannot-be-null-parameter-name-connectionstring-appsettings-json-in-start

Answer 1

First of all, the

 "Data": {
"ConnectionStrings": {
  "DefaultConnection": "Data Source=server;Initial Catalog=dbase;Trusted_Connection=True;MultipleActiveResultSets=true"},
}

Is slightly different from the structure you get when you add a "Asp.NET Configuration File" in Visual Studio. When you do that you get

"ConnectionStrings": {
  "DefaultConnection": "Data Source=server;Initial Catalog=dbase;Trusted_Connection=True;MultipleActiveResultSets=true"},

without the "Data" JavaScript Object. So that's why the extension method isn't working. It expects this structure. You can use this structure (the one with "Data") anyway and get your connection string like so:

var connectionString = Configuration["Data:ConnectionStrings:DefaultConnection"];

Notice that you are navigating through the JavaScript object tree using : instead of .. That's due to some cross-platform issues with using the ..

If you edit out the "Data":{} you can do this :

var connectionString = Configuration["ConnectionStrings:DefaultConnection"];

Now the extension method will work. Underneath the Microsoft extensions it is the same thing as the code above.

var config2 = Configuration.GetConnectionString("DefaultConnection");