相关疑难解决方法(0)

添加迁移时,包管理器控制台中出现以下错误

值不能为空.参数名称: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 …