asp.net core 2.0-值不能为null.参数名称:connectionString [英] asp.net core 2.0 - Value cannot be null. Parameter name: connectionString

问题描述

添加迁移时，程序包管理器控制台中出现以下错误

I had the following error in package manager console when Add-Migration

值不能为null.参数名称:connectionString

Value cannot be null. Parameter name: connectionString

这是我的创业公司

namespace MyProject
{
    public class Startup
    {
        public IConfiguration Configuration { get; set; }
        public Startup(IConfiguration config)
        {
            Configuration = config;
        }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContextPool<AppDbContext>(options =>
                             options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
            services.AddTransient<IDevRepo, DevRepo>();
            services.AddMvc();
            services.AddMemoryCache();
            services.AddSession();
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            app.UseStatusCodePages();
            app.UseStaticFiles();
            app.UseMvcWithDefaultRoute();
            app.Run(async (context) =>
            {
                await context.Response.WriteAsync(Configuration["Message"]);
            });
        }
    }
}

程序类:

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

    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .ConfigureAppConfiguration((context, builder) => builder.SetBasePath(context.HostingEnvironment.ContentRootPath)
                       .AddJsonFile("appsettings.json")
                       .Build())

            .UseStartup<Startup>()
            .Build();
}

appsettings.json:

appsettings.json:

{
  "Message": "Hello World",
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=NotMyFault;Trusted_Connection=True;MultipleActiveResultSets=true"
  }
}

有趣的是，如果我运行该应用程序，它将显示"Hello World"，但是在添加迁移时，它找不到connectionString.有人可以在这里点灯吗?谢谢.

Interestingly if I run the app, it displays "Hello World", but when add migration it cannot find connectionString. Can someone please shed some lights here? Thanks.

推荐答案

我发现了自己的问题.

我有一个AppDbContextFactory类，该类继承了IDesignTimeDbContextFactory.删除此类可解决此问题.

I have an AppDbContextFactory class which inherits IDesignTimeDbContextFactory. Deleting this class resolves this issue.

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