Database Initialization in Entity Framework 6

We have seen that Code-First creates a database automatically in the Simple Code First Example section. Here, we will learn how EF decides the database name and server while initializing a database in code-first approach.

The following figure shows a database initialization workflow, based on the parameter passed in the base constructor of the context class, which is derived from DbContext:

As per the above figure, the base constructor of the context class can have the following parameter.

1. No Parameter
2. Database Name
3. Connection String Name

No Parameter

If you do not specify the parameter in the base constructor of the context class then it creates a database in your local SQLEXPRESS server with a name that matches your {Namespace}.{Context class name}. For example, EF will create a database named SchoolDataLayer.Context for the following context class:

namespace SchoolDataLayer
{
    public class Context: DbContext 
    {
        public Context(): base()
        {
            
        }
    }
}

Database Name

You can also specify the database name as a parameter in a base constructor of the context class. If you specify a database name parameter, then Code First creates a database with the name you specified in the base constructor in the local SQLEXPRESS database server. For example, Code First will create a database named MySchoolDB for the following context class.

namespace SchoolDataLayer
{
    public class Context: DbContext 
    {
        public Context(): base("MySchoolDB") 
        {
                   
        }
    }
}
        

ConnectionString Name

You can also define the connection string in app.config or web.config and specify the connection string name starting with "name=" in the base constructor of the context class. Consider the following example where we pass the name=SchoolDBConnectionString parameter in the base constructor.

namespace SchoolDataLayer
{
    public class Context: DbContext 
    {
        public SchoolDBContext() : base("name=SchoolDBConnectionString") 
        {
        }
    }
}

App.config:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <connectionStrings>
    <add name="SchoolDBConnectionString" 
    connectionString="Data Source=.;Initial Catalog=SchoolDB-ByConnectionString;Integrated Security=true" 
    providerName="System.Data.SqlClient"/>
    </connectionStrings>
</configuration>

In the above context class, we specify a connection string name as a parameter. Please note that the connection string name should start with "name=", otherwise it will consider it as a database name. The database name in the connection string in app.config is SchoolDB-ByConnectionString. EF will create a new SchoolDB-ByConnectionString database or use the existing SchoolDB-ByConnectionString database in the local SQL Server. Make sure that you include providerName = "System.Data.SqlClient" for the SQL Server database in the connection string.