Below is how you can provide the entire configuration in the codebase for EF models and how to provide the connection strings at runtime. I recently struggled with this too because documentation on this is a little hard to find.
Let's assume you generated your model from your database (DB-First): MyEntities.edmx
You will have a partial class in your project such as this:
public partial class MyEntities : DbContext
{
public MyEntities ()
: base("name=MyEntities")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
throw new UnintentionalCodeFirstException();
}
public virtual DbSet<MyTable> MyTable { get; set; }
}
When you generated your model in VS, if you selected to store the connection string in the config file the automatic code generation will put the connection string config name in the constructor as it is above: public MyEntities(): base("name=MyEntities")
And in the config of your project you will have something like:
<configuration>
<connectionStrings>
<add name="MyEntities" connectionString="metadata=res://MyProject/MyEntities.csdl|res://MyProject/MyEntities.ssdl|res://MyProject/MyExchangeEntities.msl;provider=System.Data.SqlClient;provider connection string='data source=SERVERADDRESS;initial catalog=DATABASENAME;persist security info=True;user id=USERID;password=PASSWORD;MultipleActiveResultSets=True;App=EntityFramework'" />
</connectionStrings>
</configuration>
Now to bypass this, if you take a look at the DbContext constructor: public DbContext(string nameOrConnectionString); it actually says you can pass the connection string directly to it.
So all that you need to do is to extend this partial class and add another constructor that takes a connectionstring.
public partial class MyEntities
{
/// <summary>
/// This constructor allows us to pass connection strings at runtime
/// </summary>
/// <param name="connectionString">Entity Framework connection string</param>
public MyEntities(string connectionString) : base(connectionString)
{
}
}
Even though it is obvious, I just want to mention that we extend the partial class instead of modifying the auto generated one so it doesn't get overwritten when we re-generate the model in the future.
To connect using your connection string you simply construct your object like this: new MyEntities("metadata=res://MyProject/MyEntities.csdl|res://MyProject/MyEntities.ssdl|res://MyProject/MyExchangeEntities.msl;provider=System.Data.SqlClient;provider connection string='data source=SERVERADDRESS;initial catalog=DATABASENAME;persist security info=True;user id=USERID;password=PASSWORD;MultipleActiveResultSets=True;App=EntityFramework'");
And finally, if you want to provide the EF configuration in the codebase as well, it can be done like this:
/// DbConfiguration belongs to System.Data
public class EntityFrameworkConfig : DbConfiguration
{
public EntityFrameworkConfig()
{
//We set configurations for entity framework here so that we don't have to add it in the app.config
this.SetDefaultConnectionFactory(new SqlConnectionFactory());
this.SetProviderServices(SqlProviderServices.ProviderInvariantName, SqlProviderServices.Instance);
}
}
/// <summary>
/// This class with the DbConfigurationType attribute allows EntityFramework to know
/// to get its config from the EntityFrameworkConfig class instead of the app.config
/// </summary>
[DbConfigurationType(typeof(EntityFrameworkConfig))]
public partial class MyEntities
{
/// <summary>
/// This constructor allows us to pass connection strings at runtime
/// </summary>
/// <param name="connectionString">Entity Framework connection string</param>
public MyEntities(string connectionString) : base(connectionString)
{
}
}
