zoukankan      html  css  js  c++  java
  • AddDbContext was called with configuration, but the context type 'NewsContext' only declares a parameterless constructor?

    问题

    An error occurred while starting the application.
    
    ArgumentException: AddDbContext was called with configuration, but the context type 'NewsContext' only declares a parameterless constructor. This means that the configuration passed to AddDbContext will never be used. If configuration is passed to AddDbContext, then 'NewsContext' should declare a constructor that accepts a DbContextOptions<NewsContext> and must pass it to the base constructor for DbContext.
    Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.CheckContextConstructors<TContext>()
    
    ArgumentException: AddDbContext was called with configuration, but the context type 'NewsContext' only declares a parameterless constructor. This means that the configuration passed to AddDbContext will never be used. If configuration is passed to AddDbContext, then 'NewsContext' should declare a constructor that accepts a DbContextOptions<NewsContext> and must pass it to the base constructor for DbContext.
    Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.CheckContextConstructors<TContext>()
    Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.AddDbContext<TContextService, TContextImplementation>(IServiceCollection serviceCollection, Action<IServiceProvider, DbContextOptionsBuilder> optionsAction, ServiceLifetime contextLifetime, ServiceLifetime optionsLifetime)
    Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.AddDbContext<TContextService, TContextImplementation>(IServiceCollection serviceCollection, Action<DbContextOptionsBuilder> optionsAction, ServiceLifetime contextLifetime, ServiceLifetime optionsLifetime)
    Microsoft.Extensions.DependencyInjection.EntityFrameworkServiceCollectionExtensions.AddDbContext<TContext>(IServiceCollection serviceCollection, Action<DbContextOptionsBuilder> optionsAction, ServiceLifetime contextLifetime, ServiceLifetime optionsLifetime)
    News.Startup.ConfigureServices(IServiceCollection services) in Startup.cs
    +
                services.AddDbContext<NewsContext>(options =>
    Microsoft.AspNetCore.Hosting.ConventionBasedStartup.ConfigureServices(IServiceCollection services)
    Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices()
    Microsoft.AspNetCore.Hosting.Internal.WebHost.Initialize()
    Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()

    原因

    NewsContext.cs

    using Microsoft.EntityFrameworkCore;
    
    namespace News.Service
    {
        public class NewsContext : DbContext
        {
            public DbSet<News.Model.Entity.News> News { get; set; }
            public DbSet<News.Model.Entity.Banner> Banner { get; set; }
            public DbSet<News.Model.Entity.Comment> Comment { get; set; }
            public DbSet<News.Model.Entity.NewsClassify> NewsClassify { get; set; }
        }
    }

    Startup.cs

     public void ConfigureServices(IServiceCollection services)
            {
                ......
    
                services.AddDbContext<NewsContext>(options =>
                {
                  options.UseSqlServer(Configuration.GetConnectionString("MsSqlConnection"), db => db.UseRowNumberForPaging());
                });
    
                ......
    
            }

    该错误表示,如果通过AddDbContext配置NewsContext,那么需要添加一个DbContextOptions<NewsContext>类型参数的构造函数到NewsContext类。否则.net core 不能注入时带上AddDbContext添加的配置

    解决方法

    如上面所说,NewsContext类添加一个DbContextOptions<NewsContext>类型参数的构造函数

    using Microsoft.EntityFrameworkCore;
    
    namespace News.Service
    {
        public class NewsContext : DbContext
        {
            public NewsContext(DbContextOptions<NewsContext> options) : base(options)
            {
            }
    
            public DbSet<News.Model.Entity.News> News { get; set; }
            public DbSet<News.Model.Entity.Banner> Banner { get; set; }
            public DbSet<News.Model.Entity.Comment> Comment { get; set; }
            public DbSet<News.Model.Entity.NewsClassify> NewsClassify { get; set; }
        }
    }
  • 相关阅读:
    Centos安装webbench
    schema://host[:port#]/path/.../[?query-string][#anchor]
    ab压力测试报错: apr_socket_recv: Connection reset by peer (104)
    Nginx配置proxy_pass转发的/路径问题
    压力测试的轻量级具体做法
    jquery删除动态增加的li
    css如何li中选中后加上class属性js控制
    JQuery中两个ul标签的li互相移动实现方法
    xcode生成的IOS安装文件的位置
    xcode生成文件路径
  • 原文地址:https://www.cnblogs.com/Zev_Fung/p/10089974.html
Copyright © 2011-2022 走看看