How to place a connection string to a json configuration file using .NET Core Configuration framework?

Question

My solution has 3 project:

• Entity(include Dbcontext,...), target framwork .NetStandard 1.4, project type library
• WebApi
• WebUi

i want to create function migrate into Entity Project. In Entity project, i have a class TemporaryDbContextFactory

public class TemporaryDbContextFactory : IDbContextFactory<MyContext>
    {


        public ApplicationContext Create(DbContextFactoryOptions options)
        {
            var builder = new DbContextOptionsBuilder<MyContext>();
            builder.UseSqlServer("Server=(local)\\mssqllocaldb;Database=mydatabase;Trusted_Connection=True;MultipleActiveResultSets=true;User ID=sa; Password=123456",
                optionsBuilder => optionsBuilder.MigrationsAssembly(typeof(MyContext).GetTypeInfo().Assembly.GetName().Name));
            return new MyContext(builder.Options);
        }
    }

but in here i don't want to use hardcode connection string i tried to create appsetting for dynamic connection string :

public class MyContextFactory : IDbContextFactory<ApplicationContext>
    {
        public MyContext Create()
        {
            var environmentName =
                        Environment.GetEnvironmentVariable(
                            "Hosting:Environment");

            var basePath = AppContext.BaseDirectory;

            return Create(basePath, environmentName);
        }

        public MyContext Create(DbContextFactoryOptions options)
        {
            return Create(
                options.ContentRootPath,
                options.EnvironmentName);
        }

        private MyContext Create(string basePath, string environmentName)
        {
            var configuration = new Configuration();
            configuration.AddJsonFile(“config.json”);
            var emailAddress = configuration.Get("emailAddress");

            var builder = new ConfigurationBuilder()
                .SetBasePath(basePath)
                .AddJsonFile("appsettings.json")
                .AddJsonFile($"appsettings.{environmentName}.json", true)
                .AddEnvironmentVariables();


            var config = builder.Build();

            var connstr = config.GetConnectionString("(default)");

            if (String.IsNullOrWhiteSpace(connstr) == true)
            {
                throw new InvalidOperationException(
                    "Could not find a connection string named '(default)'.");
            }
            else
            {
                return Create(connstr);
            }
        }

        private MyContext Create(string connectionString)
        {
            if (string.IsNullOrEmpty(connectionString))
                throw new ArgumentException(
                    $"{nameof(connectionString)} is null or empty.",
                    nameof(connectionString));

            var optionsBuilder =
                new DbContextOptionsBuilder<MyContext>();

            optionsBuilder.UseSqlServer(connectionString);

            return new MyContext(optionsBuilder.Options);
        }
    }

i stuck in create a instance of this

var configuration = new Configuration();

the entity project doesn't have any reference to Microsoft.Extensions.Configuration I don't know how to add this because of I can't find it. please help me add this reference or suggest me a different way

Answer 1

This is a new configuration framework which you'll like after get used to it:

var configuration = new ConfigurationBuilder()
   .AddJsonFile("config.json")
   .Build();
var emailAddress = configuration.GetValue<string>("emailAddress");

You'll need the following nuget packages to be installed: Microsoft.Extensions.Configuration.Json Microsoft.Extensions.Configuration.ConfigurationBinder

If you don't see it, be sure you're using the right feed. Look at Package Source combobox of a Package Manager, it should be nuget.org.

Also, be sure that config.json configuration file is copied to the output:

{
   "emailAddress" : "[email protected]"
}

Regarding connection strings specifically, look at this sample: https://learn.microsoft.com/en-us/ef/core/miscellaneous/connection-strings#aspnet-core