寻找对这个问题的一些见解。对我来说，看起来所有的配置都符合预期，但是每当我尝试运行 dotnet publish TestAPI.dll 并试图击中一个端点，我看到以下内容：
argumentnullexception:值不能为null。参数名称：connectionstring microsoft.entityframeworkcore.utilities.check.NoteEmpty（字符串值，字符串参数名称）microsoft.entityframeworkcore.infrastructure.relationaloptionsextension.withconnectionstring（字符串连接字符串）microsoft.entityframeworkcore.mysqldbcontextoptionsextensions.usemysql（dbcontextoptionsbuilder选项生成器，字符串连接字符串，action mysqloptionsaction）testapi.startup.b_uu4_0（dbcontextoptionsbuilder options）在startup.cs+options.usemysql（configuration.getconnectionstring（“defaultconnection”））；microsoft.extensions.dependencyinjection.entityframeworkservicecollectionextensions+<>c\u displayclass0\u 0.b\u 0（iserviceprovider p，dbcontextoptionsbuilder b）microsoft.extensions.dependencyinjection.entityframeworkservicecollectionextensions.dbcontextoptionsfactory（iserviceprovider applicationserviceprovider，操作选项action）microsoft.extensions.dependencyinjection.entityframeworkservicecollectionextensions+<>c\u displayclass5\u 0.b\u 0（iserviceprovider p）microsoft.extensions.dependencyinjection.servicelookup.callsiteruntimeresolver.visitfactory（factorycallsite factorycallsite，serviceprovider）microsoft.extensions.dependencyinjection.servicelookup.callsitevisitor.visitcallsite（iservicecallsite callsite，Target参数）
当我从ide（visualstudioformac）运行应用程序时，我可以确认它是否按预期工作。以下是我的相关配置：
appsettings.json文件

{
  "ConnectionStrings": {
    "DefaultConnection": "server=localhost;userid=root;pwd=root;port=3306;database=Expenses;sslmode=none;"
  },
  "Logging": {
    "IncludeScopes": false,
    "Debug": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
    //"Console": {
    //  "LogLevel": {
    //    "Default": "Warning"
    //  }
    //}
  }
}

appsettings.development.json文件

{
  "ConnectionStrings": {
    "DefaultConnection": "server=localhost;userid=root;pwd=root;port=3306;database=Expenses;sslmode=none;"
  },
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  }
}

启动.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using TestAPI.Data;
using TestAPI.Data.Models;
using System;
using Microsoft.Extensions.Logging;

namespace TestAPI
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCors();

            services.AddMvc();

            services.AddDbContext<ExpensesDbContext>(options =>
                                                    options.UseMySQL(Configuration.GetConnectionString("DefaultConnection")));
            services.AddTransient<IBaseDa<Accounts>, AccountsDataAccess>();
            services.AddTransient<IExpensesDa, ExpensesDa>();
        }

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

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseCors(builder => builder
                .AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader()
                .AllowCredentials());

            app.UseMvc();
        }
    }
}

程序.cs

using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;

namespace TestAPI
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //var builder = new ContainerBuilder();

            //// register types here for DI
            //builder.RegisterType<AccountsDataAccess>().As<IBaseDa<Accounts>>();

            //_container = builder.Build();

            BuildWebHost(args).Run();
        }

        public static IWebHost BuildWebHost(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .Build();
    }
}

甚至尝试在相应的发布文件夹（例如bin/release/netcoreapp2.0/publish）中编辑appsettings.development.json和appsettings.json
非常感谢您的帮助！谢谢大家