我无法在 .NET Core 2.2 Razor Pages 的 DbContext 类中检索连接字符串

Question

在 Startup.cs 中配置服务这有效：

var connection = Configuration["ConnectionStrings:DefaultConnection"];

        services.AddDbContext<MyDbContext>(
                 options => { options.UseSqlServer(connection); });

在我的 MyDbContext.cs 类中这不起作用：

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;

using OESAC.Models;

namespace OESAC.Models
{
    public class MyDbContext : DbContext
    {
        public MyDbContext(DbContextOptions<MyDbContext> options)
        : base(options)
        { }

        public DbSet<Courses> Courses { get; set; }
        public DbSet<Sponsors> Sponsors{ get; set; }

        public IConfiguration Configuration { get; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {

           var connection = Configuration["ConnectionStrings:DefaultConnection"];

            optionsBuilder.UseSqlServer(connection);

            ;
        }


    }
}

我可以对连接字符串进行硬编码，但我希望它根据我的 appSettings.Development.json 和 appSettngs.json（生产）动态更改。我不敢相信我花了这么多时间试图弄清楚这一点。它让我付出的代价远远超过了我得到的报酬。

Answer 1

您需要在构造函数中注入IConfiguration 才能访问配置。

public class MyDbContext : DbContext
{
    private readonly IConfiguration _configuration;

    public MyDbContext(IConfiguration configuration)       
    {
       _configuration = configuration
    }

    public DbSet<Courses> Courses { get; set; }
    public DbSet<Sponsors> Sponsors{ get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {

       var connection = _configuration["ConnectionStrings:DefaultConnection"];

        optionsBuilder.UseSqlServer(connection);            
    }
}

Startup.cs：

services.AddDbContext<ApplicationDbContext>();