Resolved Why is startup.cs not reading database connection string from appsettings.json?

destro

Active member
Joined
Mar 28, 2020
Messages
41
Programming Experience
1-3
I faced this issue while trying to add-remove migration or updating database and took me almost a week to find a workaround. For some reason, my connection string to local SQL server wasn't being read from the appsettings.json file or appsettings.environment.json file. I looked out for many workarounds but this one solved it in my startup.cs class:


startup.cs:
services.AddDbContextPool<ApplicationDbContext>(options =>
     options.UseSqlServer("Server=(localdb)\\MSSQLLocalDB;Database=AstrologerDb;Trusted_Connection=True;MultipleActiveResultSets=true"));

Earlier it was this:

startup.cs:
   services.AddDbContextPool<ApplicationDbContext>(options =>
     options.UseSqlServer(_config["ConnectionStrings:DefaultConnection"]));

This is the error I was getting when trying to add migration with the above method:

System.ArgumentNullException: Value cannot be null.
Parameter name: connectionString
at Microsoft.EntityFrameworkCore.Utilities.Check.NotEmpty(String value, String parameterName)
at Microsoft.EntityFrameworkCore.SqlServerDbContextOptionsExtensions.UseSqlServer(DbContextOptionsBuilder optionsBuilder, String connectionString, Action`1 sqlServerOptionsAction)
at manglamastro.Startup.<ConfigureServices>b__2_0(DbContextOptionsBuilder options) in C:\Users\dell-pc\source\repos\manglamastro\manglamastro\Startup.cs:line 27
at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__DisplayClass3_0`2.<AddDbContextPool>b__0(IServiceProvider _, DbContextOptionsBuilder ob)
at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__DisplayClass5_0`2.<AddDbContextPool>b__0(IServiceProvider sp, DbContextOptionsBuilder ob)
at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.DbContextOptionsFactory[TContext](IServiceProvider applicationServiceProvider, Action`2 optionsAction)
at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__DisplayClass10_0`1.<AddCoreServices>b__0(IServiceProvider p)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitSingleton(SingletonCallSite singletonCallSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__10`1.<AddCoreServices>b__10_1(IServiceProvider p)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitSingleton(SingletonCallSite singletonCallSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitIEnumerable(IEnumerableCallSite enumerableCallSite, ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument argument)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetServices[T](IServiceProvider provider)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.FindContextTypes()
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.FindContextType(String name)
at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.RemoveMigration(String contextType, Boolean force)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.RemoveMigrationImpl(String contextType, Boolean force)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.RemoveMigration.<>c__DisplayClass0_1.<.ctor>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Value cannot be null.
Parameter name: connectionString


This is my appsettings.json file:

appsettings.json:
{
    "ConnectionStrings": {
        "DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=AstrologerDb;Trusted_Connection=True;MultipleActiveResultSets=true"
    },
    "Logging": {

        "LogLevel": {
            "Default": "Warning"
        }
    }
}


my program.cs

Program.cs:
namespace manglamastro
{
    public class Program
    {
        public static void Main(string[] args)
        {
            BuildWebHost(args).Run();
        }

        public static IWebHost BuildWebHost(string[] args)
        {
            return new WebHostBuilder()
                .UseKestrel()
                .UseContentRoot(Directory.GetCurrentDirectory())
                .UseStartup<Startup>()
                .Build();
        }
    }
}



This is startup.cs

Startup.cs:
using manglamastro.Models;
namespace manglamastro
{
    public class Startup
    {
        private IConfiguration _config;
        public Startup(IConfiguration config)
        {
            _config = config;
        }
        
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddScoped<IAstrologerRepository, SQLAstrologerRepository>();

            services.AddMvc();
            services.AddDbContextPool<ApplicationDbContext>(options =>
     options.UseSqlServer("Server=(localdb)\\MSSQLLocalDB;Database=AstrologerDb;Trusted_Connection=True;MultipleActiveResultSets=true"));
          
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
          

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                app.UseHsts();
            }
            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseAuthentication();
            app.UseCookiePolicy();

            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");

                routes.MapRoute(name: "login",
                    template: "{controller=Home}/{action=Login}");
                
            });

        }
    }
}

ApplicationDBContext that inherits from DesignTimeDbContextFactory.cs
ApplicationDbContext:
namespace manglamastro.Models
{
    public class ApplicationDbContext:DbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options):base(options)
        {

        }

        public  DbSet<Astrologer> Astrologers { get; set; }
        public DbSet<Customers> Customers { get; set; }
        public DbSet<Category> Categories { get; set; }
        public DbSet<Specialization> Specializations { get; set; }


    }
}


This is DesignTimeDbContextFactory.cs

DesignTimeDbContextFactory.cs:
namespace manglamastro.Models
{
    public class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<ApplicationDbContext>
    {
        public ApplicationDbContext CreateDbContext(string[] args)
        {
            IConfigurationRoot configuration = new ConfigurationBuilder()
           .SetBasePath(Directory.GetCurrentDirectory())
           .AddJsonFile("appsettings.json")
           .Build();
            var builder = new DbContextOptionsBuilder<ApplicationDbContext>();
            var connectionString = configuration.GetConnectionString("DefaultConnection");
            builder.UseSqlServer(connectionString);
            return new ApplicationDbContext(builder.Options);
        }
    }
}


There is only single HomeController so far and some shared view with index.cshtml.

What could have caused this issue which didn't let my startup.cs class to read from appsettings.json?

I am a beginner to this so if it's not too much can anyone help me figure this out, also how do I get my startup.cs to read connection string from appsettings.json? Can it affect my project somehow in future?

This is my project structure:

devenv_nsO2BDPWOJ.png


















Thanks in advance

 

Skydiver

Staff member
Joined
Apr 6, 2019
Messages
5,711
Location
Chesapeake, VA
Programming Experience
10+
Apparently, in .NET Core 2.0 (and up) there was an undocumented breaking change to the WebHostBuilder() which causes it not to read the appsettings.json. It looks like the quickest way to fix things is to call CreateDefaultBuilder() as per the documentation:
 
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