Question

My ASP.Net MVC application has to connect to multiple databases at run time. I can overload my class to accept the connection string at run time as shown below

class MyClassDBContext:DbContext
{
  public MyClassDBContext(string str) : base(str)
  {
    this.Database.Connection.ConnectionString = str;
  }
}

Currently, I am retrieving this connection string from a database table. My workflow is as follows

1. Website connects to default database using credentials stored in
   web.config
2. Website queries default database to get connection strings for
   other databases.
3. Websites connects to other databases by supplying the connection
   string at run time

The problem I facing right now is in keeping my code clean. Every time I need the connection string for database number 2, I have to look it up in the default database. Is there any cleaner way of doing this? I considered storing the connection string in the profile data but I am not sure if this is a good idea. Every user of my website will need to connect to at most 2-3 different databases depending on their credentials.

Answer 1

I would personally put all connection strings in your App.Config file and use a simple IOC implementation.

Actually the ninject package off Nuget might be perfect for your needs.

Here’s what I mean though. Hopefully this makes your code clean. I used this exact same pattern for a previous project and it worked out well.

You could take it a step further and make a Service Locator and register services in your global.asax. Let me know if that interests you. Also check out ninject.

public interface IService() 
{ 
  string GetConnectionString(); 
  void DoStuff(); 
}

public class DBServiceOne : DbContext, IService
{
  protected string GetConnectionString() 
  {
    return ConfigurationManager.AppSettings["DBServiceOneConnectionString"]
  }

  public DBServiceOne(string str) : base(str)
  {
     this.Database.Connection.ConnectionString = GetConnectionString()
  }

   public void DoStuff() { //logic goes here }
}

public class DBServiceTwo : DbContext, IService
{

    public DBServiceTwo(string str) : base(str)
    {
      this.Database.Connection.ConnectionString = GetConnectionString();
    }


    protected string GetConnectionString() 
    {
      return ConfigurationManager.AppSettings["DBServiceTwoConnectionString"]
    }

    public void DoStuff() { //logic goes here }
}

public class DBServiceThree : DbContext, IService
{

   public DBServiceThree(string str) : base(str)
   {
     this.Database.Connection.ConnectionString = GetConnectionString();
   }

   protected string GetConnectionString() 
   {
     return ConfigurationManager.AppSettings["DBServiceThreeConnectionString"]
   }

   public void DoStuff() { //logic goes here }
}

Now for the implementation — Use Constructor Injection on your controllers

//This could be in your home controller

public class HomeController : AsyncController
{
    private IService DBOneService;
    private IService DBTwoService;
    private IService DBThreeService;

   public HomeController(IService one, IService two, IService three)
   {
      DBOneService= one;
      DBTwoService = two;
      DBThreeService = three;
   }

  public HomeController() : this(new DBServiceOne(), new DBServiceTwo(), new DBServiceThree()) {}

public ActionResult Index() {
   DBOneService.DoStuff(); //here you'd want to return a list of data and serialize down with json or populate your razor template with it. Hope this helps!

}