EF core is introduced us to automated migration, using it we don’t have to do database migration manually for each and every change which you make in your domain classes.

It is built by just executing the one command “enable-migration” in the CLR or also in the Package manager console.

The Code-base migration is provided more and deep control on the migration and it also allows you to configure additional things like setting a by the default value of any column and configure a computed column.

To use code-based migration first, you need to execute some code in order in the Package Manager Console in Visual Studio:

To use the Code Based migration you firstly need to execute the command “enable-migration” in the console.

Just assume you have created a normal Entity framework core application that has the following simple model:

public class Employee
{
    public int EmployeeId{ get; set; }
    public string EmployeeName{ get; set; }
}
				

During your application development period, you have the option to drop and create API and changing your models but now the application is in the production phase. In this phase you can take care of schema and data you work without losing the data and schema or any other database object.

For using migration, you need to install some packages and tools first:

Generally, most of the recommendations is of using .NET core CLI tools with its platforms independent, so it is working on all platforms. But you will be more comfortable with Entity Frame Work migration and you can also do it using the Package Manager Console tool.

First, as we see above we defined the initial domain classes at this point we don’t have any database which stores our data from our domain classes. So first, we need to create a migration. Some steps are below for adding migration:

Initially, you need to open the package manager console from Tools menu in this menu NuGet Package Manager in this open Package Manager Console and execute the below command:

				  
PM>add-migration FirstMigration
				  

In the above commands, FirstMigration is the name of a migration. This will create three files in the migration folder of your project, which is shown below:

Entity framework is creating some file to your project when migration is called and it is good to know what specifically entity framework core is generated but we will skip it for now.

At this step, you need to create a database and schema using the migration and it is done like below:

Just writing the below command in your CLI or Package Manager Console tool.

				 
 PM>Update-Database
				  

You can also remove the last run migration if it is not applied to your database. You can use the below command to remove the last created migration and also for revert model snapshot.

If you use the Package Manager Console then use the below command:

				  
PM>remove-migration
				  

If you are done using CLI then use the below command:

				  
>dotnet ef migrations remove
				  

These commands will remove the last migration and revert the model snapshot to the previous migration. If the last migration is already applied to the database, then it throws the following exception.

These commands remove the last migration and also revert the model snapshot to the last migration.

NOTE : If your migration is already applied to your database then it is throwing the below error.

The migration has already been applied to the database. Revert it and try again. If the migration has been applied to other databases, consider reverting its changes using a new migration