从 appsettings.json 到 Entity Framework .NET Core 中的 OnConfiguring 方法的连接字符串

Question

如我所见，我无法通过此方法访问 IConfiguration 注入的对象。此外，正如我所见，无法访问 HttpContext 并从那里进入。有什么简单的方法可以获取存储在 appsettings.json 中的连接字符串？

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Projekt.Models;

using System.ComponentModel.DataAnnotations;
using Microsoft.AspNetCore.Http;

namespace Project.DAL
{
    public class UserContext : DbContext
    {
        
        public DbSet<User> Users {get;set;}


        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            string connection_string = ""; //connection string from appsettings.json
            optionsBuilder.UseSqlServer(connection_string);
        }
            
        public class User {
            public string login{ get; set; }
            public string password { get; set; }

            
        }
    }
}

Answer 1

据我所知，您可以在任何需要的地方注入 IConfiguration：

    private readonly IConfiguration _configuration;

    public MyClass(IConfiguration configuration)
    {
        _configuration = configuration;
    }

但是在Startup.ConfigureServices中这样做没有错：

 string connection = _configuration.GetConnectionString("Main");
 services.AddDbContext<UserContext >(options => options.UseSqlServer(connection));

Answer 2

您必须将 IConfiguration 注入 Startup 构造函数：

public class Startup
{
    public IConfiguration Configuration { get; }
    public IWebHostEnvironment Environment { get; }

    public Startup(IConfiguration configuration, IWebHostEnvironment environment)
    {
        Configuration = configuration;
        Environment = environment;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.ConfigureDatabase(Configuration);
       
        // ...other services
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
       // ...middlewares
    }
}

请注意，我使用了一种扩展方法来配置我的 dbContext，这使得 Startup 更干净：

public static class ServiceExtensions
{
    public static void ConfigureDatabase(this IServiceCollection services, IConfiguration configuration)
    {
        services.AddDbContext<MyDbContext>(options =>
        {
            string connectionString = configuration.GetConnectionString("sqlConnection") + ";password=" + configuration["Passwords:Database"];
            options.UseSqlServer(connectionString);
        });
    }
}

Answer 3

首先，您必须在 appsettings.json

中设置连接字符串

"ConnectionStrings": {
"sqlConnection": "server=\SQLEXPRESS; database=AKKADatabase; Integrated Security=true"

},

而你的startup.cs你必须配置你的连接

    public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<ApplicationContext>(option => option.UseSqlServer(Configuration.GetConnectionString("sqlConnection")));
        services.AddControllersWithViews();
    }

} 在您可以在数据库上下文中使用它之后：

   public class ApplicationContext : DbContext
{
    public ApplicationContext(DbContextOptions options)
        : base(options)
    {
    }

}

从 appsettings.json 到 Entity Framework .NET Core 中的 OnConfiguring 方法的连接字符串

Connection string from appsettings.json to OnConfiguring method in Entity Framework .NET Core

.net

c#

asp.net

model-view-controller

appsettings