Question

context = new ApplicationDbContext();
context.Clients.Add(item);

InvalidOperationException：未配置任何数据库提供程序对于这个DbContext。可以通过覆盖提供程序来配置提供程序 DbContext.OnConfiguring方法或者使用AddDbContext 应用服务提供商。如果使用AddDbContext，那么也确保您的DbContext类型接受DbContextOptions 对象在其构造函数中并将其传递给基础构造函数的DbContext。

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
            : base(options)
        {

        }

        public ApplicationDbContext()
        {

        }

        protected override void OnModelCreating(ModelBuilder builder)
        {
            base.OnModelCreating(builder);

        }

        public DbSet<Client> Clients { get; set; }

启动

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);

            if (env.IsDevelopment())
            {
                // For more details on using the user secret store see https://go.microsoft.com/fwlink/?LinkID=532709
                builder.AddUserSecrets<Startup>();
            }

            builder.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.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

            services.AddIdentity<ApplicationUser, IdentityRole>()
                .AddEntityFrameworkStores<ApplicationDbContext>()
                .AddDefaultTokenProviders();

            services.AddMvc();

            // Add application services.
            services.AddTransient<IEmailSender, AuthMessageSender>();
            services.AddTransient<ISmsSender, AuthMessageSender>();
        }

        // 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();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseDatabaseErrorPage();
                app.UseBrowserLink();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            app.UseStaticFiles();

            app.UseIdentity();

            // Add external authentication middleware below. To configure them please see https://go.microsoft.com/fwlink/?LinkID=532715

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

已更新

我添加了

// Startup.ConfigureServices
public void ConfigureServices(IServiceCollection services)
    {
        // Add framework services.
        services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        //////my=>
        services.AddDbContext<DbContext>(config =>
        {
            config.UseSqlServer(Configuration.GetConnectionString("Default"));
        });

并在appsettings.json中配置它

    {
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=aspnet-WebApplicationCore-42a4ac05-477c-4ea7-b286-87423170b48a;Trusted_Connection=True;MultipleActiveResultSets=true",
    "Default": "Server=(localdb)\\mssqllocaldb;Database=aspnet-WebApplicationCore-42a4ac05-477c-4ea7-b286-87423170b48a;"
  },
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Warning"
    }
  }
}

我点击appsettings.json文件并将属性窗口中的属性更改为“Build Action：Content”和“CopyToOutputDirectory：Always Always”

<ItemGroup>
  <Content Update="appsettings.json">
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Content>
</ItemGroup>

错误未修复

新错误：

var result = await _userManager.CreateAsync(user, model.Password);

处理请求时发生未处理的异常。   SqlException：发生与网络相关或特定于实例的错误   同时建立与SQL Server的连接。服务器不是   发现或无法访问。验证实例名称是否正确   并且SQL Server配置为允许远程连接。   （提供者：SQL网络接口，错误：50 - 本地数据库运行时   发生了错误。 ВовремязапускаэкземпляраLocalDBпроизошлаошибка：   ошибказапускапроцессаSQLServer。）

System.Data.SqlClient.SqlInternalConnectionTds..ctor（DbConnectionPoolIdentity   identity，SqlConnectionString connectionOptions，object providerInfo，   bool redirectedUserInstance，SqlConnectionString   userConnectionOptions，SessionData reconnectSessionData，bool   applyTransientFaultHandling）

Answer 1

如果没有参数化构造函数或覆盖OnConfiguring，则无法实例化DbContext。

您有两种选择：

将DbContextOptions<ApplicationDbContext>通过DI传递给ApplicationDbContext。这是最简单的方法，在startup.cs中配置ApplicationDbContext并解析它（不使用new关键字!!!）

// Startup.ConfigureServices
services.AddDbContext<DbContext>(config => 
{
    config.UseSqlServer(Configuration.GetConnectionString("Default"));
});

并在appsettings.json中配置它

{
    "ConnectionStrings": {
        "Default": "YourSQLConnectionStringHere"
    }
}

少推荐，因为它需要对连接字符串进行硬编码，方法是在DbContext中配置它

public class ApplicationDbContext
{
    public ApplicationDbContext(DbContextOptions options) : base(options) 
    {
    }

    // The call of the base constructor via ": base()" is still required
    public ApplicationDbContext(DbContextOptions options) : base() 
    {
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(Configuration.GetConnectionString("connectionStringHere"));
        base.OnConfiguring(optionsBuilder);
    }
}

更新

在回复评论时，您需要添加

<ItemGroup>
  <Content Update="appsettings.json">
    <CopyToOutputDirectory>Always</CopyToOutputDirectory>
  </Content>
</ItemGroup>

以便将appsettings.json复制到输出目录。或者只需单击appsettings.json文件并将属性窗口中的属性更改为“Build Action：Content”和“CopyToOutputDirectory：Always Always”

InvalidOperationException：没有为此DbContext配置数据库提供程序

1 个答案:

更新