c# - 尚未为此 DbContext 配置数据库提供程序以获取 Asp.net Core 中的方法

Question

我通过 Asp.net 核心创建了一个 web api 项目，并向其中添加了一个 api Controller (名称为 BlogController)，在博客 Controller 中我有一个 get 方法 GetAllBlog 这是我的 Controller :

[Route("api/[controller]")]
public class BlogController : Controller
{
    private static Logger logger = LogManager.GetCurrentClassLogger();

    public IContext _context { get; set; }
    public BlogController(IContext ctx)
    {
        _context = ctx;
    }

    [HttpGet]
    public IEnumerable<Blog> GetAllBlog()
    {
        return _context.Blogs.ToList();
    }
 }

这是我的 IContext 和模型:

public interface IContext : IDisposable
{
    DbSet<Blog> Blogs { get; set; }
    DbSet<Post> Posts { get; set; }
    int SaveChanges();
}

和上下文:

public class Context : DbContext, IContext
{
    public Context(DbContextOptions<Context> options) : base(options)
    { }
    public virtual DbSet<Blog> Blogs { get; set; }
    public virtual DbSet<Post> Posts { get; set; }
}

和模型:

public class Blog
{
    public int BlogId { get; set; }
    public string Name { get; set; }
    public string Url { get; set; }
    public DateTime? CreationDate { get; set; }
    public virtual IList<Post> Posts { get; set; }
}

当我调用 GetAllBlog() 时，我得到了这个错误:

No database provider has been configured for this DbContext. A provider can be configured by overriding the DbContext.OnConfiguring method or by using AddDbContext on the application service provider. If AddDbContext is used, then also ensure that your DbContext type accepts a DbContextOptions object in its constructor and passes it to the base constructor for DbContext. what is the problem?

更新:这是 Startup 类中的 configurationservice 方法:

public void ConfigureServices(IServiceCollection services)
{
    var connection = @"Data Source=.;Initial Catalog=RestfullServices;Integrated Security=true";
    services.AddDbContext<Context>(options => options.UseSqlServer(connection));
    services.AddScoped<IContext>(p => new Context(new DbContextOptions<Context>()));
    services.AddApplicationInsightsTelemetry(Configuration);
    services.AddMvc();
}

Answer 1

配置DbContext时

services.AddDbContext<Context>(options => options.UseSqlServer(connection));

您将其配置为使用特定选项 options.UseSqlServer(connection)

但是在配置作用域上下文抽象时

services.AddScoped<IContext>(p => new Context(new DbContextOptions<Context>()));

正在创建一个新的 Context，其配置与之前的配置完全不同。

通过像这样在启动期间更改 IContext 向 DI 框架注册的方式

services.AddScoped<IContext, Context>();

当创建 Context 实例时，DI 框架将使用 AddDbContext 配置，在创建 DbContext 实例时，它将具有您希望从启动配置中使用的选项.

Startup.ConfigurServices 最终看起来像这样...

public void ConfigureServices(IServiceCollection services) {
    var connection = @"Data Source=.;Initial Catalog=RestfullServices;Integrated Security=true";
    services.AddDbContext<Context>(options => options.UseSqlServer(connection));
    services.AddScoped<IContext, Context>();
    services.AddApplicationInsightsTelemetry(Configuration);
    services.AddMvc();
}