Question

我一直在关注https://docs.microsoft.com/en-us/ef/core/get-started/aspnetcore/existing-db创建项目的步骤，当我到达脚手架的最后一步为我的一个实体构建一个控制器时，我得到错误＆＃34;没有为此定义无参数构造函数对象＆＃34 ;.我已经查看了stackoverflow中完全相同的问题ASP.NET MVC: No parameterless constructor defined for this object的链接，但我有一个无参数构造函数，如下面的代码所示。

public class Startup
{
    public Startup(IHostingEnvironment env)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
            .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
            .AddEnvironmentVariables();
        Configuration = builder.Build();
    }

    public IConfigurationRoot Configuration { get; }

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

        var connection = "connection string here";
        services.AddDbContext<SchoolManagementContext>(options => options.UseSqlServer(connection));
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        loggerFactory.AddConsole(Configuration.GetSection("Logging"));
        loggerFactory.AddDebug();

        app.UseMvc();
    }

}

}

Program.cs的

 var host = new WebHostBuilder()
          .UseKestrel()
          .UseContentRoot(Directory.GetCurrentDirectory())
          .UseIISIntegration()
          .UseStartup<Startup>()
          .UseApplicationInsights()
          .Build();
           host.Run();

Answer 1

答案是我更新到.Net Core 2.0，我的 program.cs 仍在使用涉及1.0的格式。我将代码更改为以下内容，我能够成功创建控制器。

更改自：

          var host = new WebHostBuilder()
              .UseKestrel()
              .UseContentRoot(Directory.GetCurrentDirectory())
              .UseIISIntegration()
              .UseStartup<Startup>()
              .UseApplicationInsights()
              .Build();
               host.Run();

TO：

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

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

MVC没有为此对象定义的无参数构造函数

1 个答案: