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)
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show some code in a minimal reproducible example that better explains what you are trying to say. Right now it is unclear what you're asking. Read How to AskNkosi– Nkosi2017-09-12 14:41:33 +00:00Commented Sep 12, 2017 at 14:41
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2 Answers
One way is to use the factory pattern, i.e. creating a service that will be used to create new instances of your context.
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);
}
}
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();
}
}
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...
1 Comment
JGreasley
This answer got me to solve my own solution working with .net core 2.1 / signalr core and needed to setup a dbContextFactory as normal dbContext gets disposed inside a hub. The only minor update needed here (for later versions) is now we call
IDesignTimeDbContextFactory, instead of IDbContextFactory. More information can be found here: https://learn.microsoft.com/en-us/ef/core/miscellaneous/cli/dbcontext-creationUse new YourContext(new DbContextOptionsBuilder<YourContext>().Use...().Options)
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