迁移期间发生错误 System.ArgumentNullException：值不能为空。（参数'connectionString'）

Question

我有如下一段代码

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;
    }
}
}

在我的 Program.cs 中，我有以下内容

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>();
                    });
        }
    }

我在 CentOs7 上做了一个发布。当我运行我的应用程序使用命令时：

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

我有以下错误：

[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:\dev\xxx\MyService\Extensions\ApplicationServiceExtentions.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:\dev\xxx\MyService\Program.cs:line 26

我不明白为什么当我在应用程序中直接硬编码时我的连接字符串的值为空。

可能是什么问题？

Answer 1

下面这行是不正确的：

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

当前它正在配置中查找具有 KEY“server=l...”的连接字符串。

如果您是硬编码，请删除 config.GetConnectionString 方法并将字符串传递给 UseMySQL:

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

或者，如果以更标准的方式进行，请使用键值对将连接字符串添加到配置文件并传递键值，例如：

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

迁移期间发生错误 System.ArgumentNullException：值不能为空。（参数'connectionString'）

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

c#

linux

.net-core

centos7

connection-string

迁移期间发生错误 System.ArgumentNullException：值不能为空。 （参数'connectionString'）

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

c#

linux

.net-core

centos7

connection-string

迁移期间发生错误 System.ArgumentNullException：值不能为空。（参数'connectionString'）