Change the connection string dynamically (per request) on Entity Framework 7 / MVC 6

Question

I have a MVC 6 application on which I need to connect to a different database (i.e. physical file but same schema) depending on who is accessing to it. That is: each customer of the web application will have it's data isolated in an SQL database (on Azure, with different performances, price levels, etc.) but all those databases will share the same relational schema and of course, the Entity Framework context class.

var cadConexion = @"Server=(localdb)\mssqllocaldb;Database=DBforCustomer1;Trusted_Connection=True;";
services.AddEntityFramework().AddSqlServer().AddDbContext<DAL.ContextoBD>(options => options.UseSqlServer(cadConexion));

The problem is that if I register the service this way I've tied it to a concrete database for a concrete customer, and I don't know if I can change latter when the middleware execution starts (this would be a good point as I can know then who is ringing at the door).

I know I can construct the Database Context passing the connection string as a parameter but this would imply that I should be creating the Database Context at runtime (early in the pipeline) for every request adn I don't know if this could be potentially unefficient or a bad practice. Furthermore I think this way I can't register the Database Context as a service for injecting it on my controllers...

What is the correct approach for this? Anybody has a similar configuration working on production?

Thanks in advance

Answer 1

First of all, I do not recommend swapping connection strings per request.

But that's not the question. You can do this. You will need to pass your DbContext a new connection string.

.AddDbContext caches the connection string in the dependency injection container, so you cannot use DI to make this scenario work. Instead, you will need to instantiate your DbContext yourself and pass it a new connection string.

Answer 2

I would have preferred not to answer my own question, but I feel that I must offer guidance to those with a similar problem, after a long and deep research over internet so I can save them a lot of time testing multi-connection scenarios, wich is quite laborious...

I've finally used a (very recent) feature and APIs of Azure called "Elastic Database Tools" wich, to be concise, is a set of tools from Microsoft aimed to address this concrete problem, specially for SaaS (software as a service) scenarios (as mine is).

Here is a good link to start with:

https://azure.microsoft.com/en-us/documentation/articles/sql-database-elastic-scale-get-started/

Good luck with your projects!