如何从Asp.Net Core中的DBContext文件中的appsettings.json中读取连接字符串? [英] How to read connection string from appsettings.json in a DBContext file in Asp.Net Core?

问题描述

我在appsettings.json文件中定义了一个连接字符串.现在我想在我的TextDBConext文件中阅读它，该怎么办?

I have defined a connection string in the appsettings.json file. now I want to read it in my TextDBConext file, how can I do it?

public class TestContext: DbContext
    {
        public DbSet<TestTable> TestTable { get; set; }
        public TestContext()
        {
        }
        public IConfiguration Configuration { get; }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer("Connection string"); //I have hardcoded here, but I want from appsettings.json
        }
    }

Appsettings.json文件:

{
  "Logging": {
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "connection_string": "Connection String"
  }
}

推荐答案

您可以在启动文件中设置数据库上下文，而完全不覆盖 OnConfiguring .只需在DbContext类中添加采用 DbContextOptions< TContext> 的构造函数即可.此构造函数应将参数传递给 base 类的构造函数，然后在 Startup.Configure 中调用 AddDbContext< TContext> ，如下所示:

You can setup your db context in the startup file and not override OnConfiguring at all. Just add a constructor that takes DbContextOptions<TContext> to your DbContext class. This constructor should pass on the parameter to the base class' constructor, then call AddDbContext<TContext> in your Startup.Configure as follows:

// your TestContext showing constructor
public class TestContext : DbContext
{
    public TestContext(DbContextOptions<TestContext> options) : base(options){ }
}

// Then in Startup.cs
public class Startup
{
   public IConfiguration Configuration {get;}

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

   public void ConfigureServices(IServiceCollection services)
   {
       services.AddDbContext<TeamsDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("connection_string")));
   }
}

值得注意的是， AddDbContext< TContext> 方法具有重载功能，允许您根据需要将上下文的服务寿命设置为Singleton或Transient.默认值为作用域".

Worth noting is that the AddDbContext<TContext> method has overloads that allow setting the service lifetime for the context to Singleton or Transient if you so wish. The default is Scoped.

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