How to change connection string or pass custom connection string for EF Model

Question

I have three database environments, Developer, Testing and Production. To setup database with sample data i created a console app where user selects environment to setup the database. I am using Entity Framework database first but stuck with how to select instance at run time. There is only one database model is it possible to change db connection at run time?

i used following code and it throws exception.

        // Truncate all Data
        if (env.Key == ConsoleKey.D)
        {
            db.Database.Connection.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["db_dev"].ToString();
        }

Model Entities has no constructor to get Connection String..

BenjaminPaul · Accepted Answer · 2014-04-10 16:16:41Z

2

Ensure you have a constructor on your DbContext class that takes a connection string and then simply pass it to the base class (Entity Framework will do the rest)

public MyDbContext : DbContext
{
    public MyDbContext(string connectionString) : base (connectionString)
    {
    } 
}

Then when you instantiate your Context you simply pass in the connection string that you would like to use... example using your code above would be...

var connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["db_dev"].ToString();
using (var context = new MyDbContext(connectionString))
{
}

edited Apr 10, 2014 at 16:16

answered Apr 10, 2014 at 16:00

BenjaminPaul

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Comments

Michael Domashchenko · Accepted Answer · 2014-04-10 15:56:04Z

0

When you're creating your instance of database context (db variable) there should be a constructor overload that accepts a string. That's how you can set it up with your custom connection string.

If your class that inherits from the DbContext doesn't have that overload, just create it because the base class does have it.

answered Apr 10, 2014 at 15:56

Michael Domashchenko

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4 Comments

sagheer Over a year ago

No, There's no constructor that takes Connection String. So i think i should create a partial class to have a constructor that takes Connection String?

BenjaminPaul Over a year ago

See my answer below.. you simply create a constructor on your Context class that takes a string and pass it to the base class...

sagheer Over a year ago

Context class says it's auto generated class and editing may change behavior of app. Manual changes to this file will be overwritten if the code is regenerated.

BenjaminPaul Over a year ago

In that case simply create a partial class and add the constructor into that instead, same thing applies.

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