值不能为空。 参数名称：connectionString

Question

因此，我一直在研究stackoverflow并检查与我的问题有关的所有问题，所有内容都已签出，但是我仍然遇到相同的错误。

值不能为空。 参数名称：connectionString

是我运行添加迁移“初始迁移”时的结果。

这是我在Startup.cs上的代码

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.AddMvc();

        services.AddDbContext<LibraryContext>(options 
            => options.UseSqlServer(Configuration.GetConnectionString("LibraryConnection")));
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseBrowserLink();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
        }

        app.UseStaticFiles();

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });
    }

这是我在appsettings.json上的连接字符串

{
 "ConnectionString": {
   "LibraryConnection": "Server(localdb)\\MSSQLLocalDB;Database=Library_Dev;Trusted_Connection=True;MultipleActiveResultSets=true"
},
   "Logging": {
     "IncludeScopes": false,
     "LogLevel": {
       "Default": "Warning"
     }
   }
}

请注意，我有一个LibraryData项目（这是另一个项目），并且该类包含一个名为LibraryContext的类。

public class : DbContext
{
    public LibraryContext(DbContextOptions options) : base(options) { }

    public DbSet<Patron> Patrons { get; set; }
}   

根据网上的资料和问题，我已经完成了所有工作，因此我似乎找不到我在做错什么！ 有人可以帮我吗？

Answer 1

我认为您在appsettings.json中打了错字ConnectionString应该是ConnectionStrings

 { "ConnectionStrings": { "LibraryConnection": "Server(localdb)\\\\MSSQLLocalDB;Database=Library_Dev;Trusted_Connection=True;MultipleActiveResultSets=true" }, "Logging": { "IncludeScopes": false, "LogLevel": { "Default": "Warning" } } }