与多个数据库一起使用实体框架

Question

I am very new to Entity Framework. I need to do something like below;

When page loads it will display data from table1 in database1 depending on the data select from the first page it has to connect to different databases (These databases has same names. But can have slight changes). I already have a way get the connections to those different DBs.

I have no idea where should I start. Please guide me. It is good if you can provide me with basic level information and examples.

Answer 1

You would need to create a separate instance of database context for each database and specify connection string as a constructor parameter

var dbContext = new MyDbContext("<connection string>")

if there is fixed list of connection strings then they can be stored in config file and used by name like

var dbContext = new MyDbContext("Name=FirstDb")

Answer 2

You can supply the Connection String to the DbContext constructor:

var db1 = new MyContext(connectionString1);
var db2 = new MyContext(connectionString2);

and in the context:

public class MyContext : DbContext
{
    public MyContext(string cs) : base(cs) { }
}

Answer 3

you will need 2 models or context if you not using entity model. if your about to use the entity model then the wizard will ask for connection string, and you will create 2 model with 2 connection strings.

i prefer the model because it easy and you the changes in the database will handle your code in one update click