如何在ConfigureServices方法ASP.NET Core中添加数据库上下文 [英] How to add db context not in ConfigureServices method ASP.NET Core

问题描述

是否可以在外部类/方法中即时添加数据库上下文？当我运行应用程序时，没有任何连接字符串，因此我需要在输入一些信息（服务器，数据库名称等）后生成数据库。

Is there any posibility to add a db context in external class/method "on fly?" When I run the application, there is no any connection string, so I need to generate a db after typing some information(server, dbname, ect)

推荐答案

一种方法是使用工厂模式，即创建将用于创建上下文的新实例的服务。

One way is to use the factory pattern, i.e. creating a service that will be used to create new instances of your context.

这里是一个示例，这不是最终的解决方案，您需要对其进行调整，但是它应该使您对这种技术有所了解：

Here is an example, it is not a final solution and you will need to adapt it to your needs but it should give you an idea of the technique:

public interface IDbContextFactory
{
    DbContext CreateDbContext(string connectionString);
}

public class DbContextFactory : IDbContextFactory
{
    public DbContext CreateDbContext(string connectionString)
    {
        return new DbContext(connectionString);
    }
}

然后在asp.net核心中，您可以注册上下文工厂并将其注入到您的控制器中：

Then in asp.net core, you can register the context factory and inject it in your controller:

 services.AddSingleton<IDbContextFactory, DbContextFactory>();

 public class SomeController
 {
      private IDbContextFactory contextFactory;

      public SomeController(IDbContextFactory contextFactory)
      {
          this.contextFactory = contextFactory;
      }

      public IActionResult Index()
      {     
         using(var db = contextFactory.CreateDbContext("Your connection string"))    {
              //Get some data
         }
         return View();
     }
 }

除了创建DbContext之外，您还可以结合使用工厂模式使用工作单元和/或存储库模式可以更好地分离关注点，并确保始终处理上下文等。

Instead of creating a DbContext you could combine the factory pattern with the unit of work and / or repository patterns to better separate concerns and to make sure you always dispose the context, etc...

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