An Error has occured during the migrations System.ArgumentNullException: Value cannot be null. (Parameter ‘connectionString’)

I have the following piece of code

using MyService.Data;
using MyService.Helpers;
using MyService.Interfaces;
using MyService.Services;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace MyService.Extensions
{
  public  static class ApplicationServiceExtentions
  {
    public static IServiceCollection AddApplicationServices(this 
    IServiceCollection services, IConfiguration config)
    {
        
        services.AddAutoMapper(typeof(AutoMapperProfiles).Assembly);
        services.AddDbContext<DataContext>(options =>
        {

           options.UseMySQL(config.GetConnectionString("server=localhost;database= mydb;user=myuser;password=mypassw"));
        });

        return services;
    }
}
}

In my Program.cs, I have the following

using System;
    using System.Threading.Tasks;
    using Microsoft.AspNetCore.Hosting;
    using Microsoft.Extensions.Hosting;
    using Microsoft.Extensions.Logging;
    using Microsoft.Extensions.DependencyInjection;
    using MyService.Data;
    using Microsoft.EntityFrameworkCore;
    using MyService.Entities;
    using Microsoft.AspNetCore.Identity;

    namespace MyService
    {
        public class Program
        {
            public async static Task Main(string[] args)
            {
                
                //CreateHostBuilder(args).Build().Run();
                var host = CreateHostBuilder(args).Build();
                using var scope = host.Services.CreateScope();
                var services = scope.ServiceProvider;

                try
                {
                    var context = services.GetRequiredService<DataContext>();
                    var userManager = services.GetRequiredService<UserManager<AppUser>>();
                    var roleManager = services.GetRequiredService<RoleManager<AppRole>>();
                    await context.Database.MigrateAsync();
                    await Utilities.UserRoleHandlerUtilitity.UserHandler(userManager, roleManager);
                }
                catch(Exception ex)
                {
                    var logger = services.GetRequiredService<ILogger<Program>>();
                    logger.LogError(ex, "An Error has occured during the migrations");
                }

                await host.RunAsync();

            }

            public static IHostBuilder CreateHostBuilder(string[] args) =>
                Host.CreateDefaultBuilder(args)
                    .ConfigureWebHostDefaults(webBuilder =>
                    {
                        webBuilder.UseStartup<Startup>();
                    });
        }
    }

I did a publish on a CentOs7. When I am running my application using the command:

/usr/share/dotnet/dotnet /var/netcore/MyService.dll

I have the following error:

[XXXXXX@ip-xxx-xxx-xxx-xxx ~]$ /usr/share/dotnet/dotnet /var/netcore/MyService.dll
   fail: MyService.Program[0]
   An Error has occured during the migrations
   System.ArgumentNullException: Value cannot be null. (Parameter 'connectionString')
     at Microsoft.EntityFrameworkCore.Utilities.Check.NotEmpty(String value, String parameterName)
     at Microsoft.EntityFrameworkCore.Infrastructure.RelationalOptionsExtension.WithConnectionString(String connectionString)
     at Microsoft.EntityFrameworkCore.MySQLDbContextOptionsExtensions.UseMySQL(DbContextOptionsBuilder optionsBuilder, String connectionString, Action`1 MySQLOptionsAction)
     at MyService.Extensions.ApplicationServiceExtentions.<>c__DisplayClass0_0.<AddApplicationServices>b__0(DbContextOptionsBuilder options) in C:devxxxMyServiceExtensionsApplicationServiceExtentions.cs:line 29
     at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__DisplayClass1_0`2.<AddDbContext>b__0(IServiceProvider p, DbContextOptionsBuilder b)
     at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.CreateDbContextOptions[TContext](IServiceProvider applicationServiceProvider, Action`2 optionsAction)
     at Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.<>c__DisplayClass17_0`1.<AddCoreServices>b__0(IServiceProvider p)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
     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__17`1.<AddCoreServices>b__17_1(IServiceProvider p)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
     at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
     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 MyService.Program.Main(String[] args) in C:devxxxMyServiceProgram.cs:line 26

I do not understand why is the value of my connection string null when I hardcoded directly it in the application.

What could be the issue?

Answer

The following line is incorrect:

options.UseMySQL(config.GetConnectionString("server=localhost;database= mydb;user=myuser;password=mypassw"));

Currently it is looking in the config for a connection string with the KEY “server=l…”.

If you are hardcoding, remove the config.GetConnectionString method and just pass in the string to UseMySQL:

options.UseMySQL("server=localhost;database= mydb;user=myuser;password=mypassw");

Or, if doing in a more standard way, add the connection string to the configuration file with a key value pair and pass the key value eg:

options.UseMySQL(config.GetConnectionString("MyDatabase"));