How to rename a database column in Entity Framework 5 Code First migrations without losing data?

Question

I got the default ASP.NET MVC 4 template successfully running with EF 5.0 Code First Migrations. However, when I update a model property name, the corresponding table column data is dropped by EF 5.0.

Is it somehow possible to rename the table column without dropping data in an automated way?

Solution 1

Manually edit the Up and Down methods of the migration to use the RenameColumn method to replace the AddColumn and DropColumn that it automatically generates for you.

Solution 2

As already said, replace the AddColumn and DropColumn that is automatically generated with RenameColumn.

Example:

namespace MyProject.Model.Migrations
{
    using System;
    using System.Data.Entity.Migrations;

    public partial class RenameMyColumn : DbMigration
    {
        public override void Up()
        {
            // Remove the following auto-generated lines
            AddColumn("dbo.MyTable", "NewColumn", c => c.String(nullable: false, maxLength: 50));
            DropColumn("dbo.MyTable", "OldColumn");

            // Add this line
            RenameColumn("dbo.MyTable", "OldColumn", "NewColumn");
        }

        public override void Down()
        {
            // Remove the following auto-generated lines
            AddColumn("dbo.MyTable", "OldColumn", c => c.String(nullable: false, maxLength: 50));
            DropColumn("dbo.MyTable", "NewColumn");

            // Add this line
            RenameColumn("dbo.MyTable", "NewColumn", "OldColumn");
        }
    }
}

Solution 3

You can get the migration to call RenameColumn for you if you do this:

[Column("NewName")]
public string OldName { get; set; }

Here is the generated migration:

    public override void Up()
    {
        RenameColumn(table: "Schema.MyTable", name: "OldName", newName: "NewName");
    }

    public override void Down()
    {
        RenameColumn(table: "Schema.MyTable", name: "NewName", newName: "OldName");
    }

If you want your property and DB column to be the same name, you can rename the property later and remove the Column attribute.

Solution 4

you have 2 steps to rename column in code first migration

1. The first step,you add ColumnAttribute above your column which are changed, and then update-database command

[Column("Content")]
public string Description { set; get; }

2. The second step,

   • add-migration yournamechange command in order to create a partial class DbMigration.

   • add into up and down method here

RenameColumn("yourDatabase","name","newName");

public override void Up()
  {
        RenameColumn("dbo.your_database", "oldColumn",          
       "newColumn");
  }


public override void Down()
  {
        RenameColumn("dbo.your_database", "newColumn", 
        "oldColumn");
  }

Because when you connect, your database and model class will communicate via name_column at database and name_type at property method in model above.

Solution 5

Now, this answer is based on my knowledge of EF4.3, so I hope the migrations work roughly the same in EF5 :) After you've created a migration, you should be able to add code in the Up and Down methods, between the dropping of the old property and the creation of the new property. This code should move the property data in the correct direction. I've solved it with the SQL() method in where you can enter raw SQL to perform the data move.

In the Up method of the migration:

SQL("update [TheTable] set [NewColumn] = [OldColumn]");

and in the Down() method:

SQL("update [TheTable] set [OldColumn] = [NewColumn]");

The disadvantage of this approach is that you might couple your code with the database you're working with at the moment (since you're writing raw DB-specific SQL). There might be other methods available for data movement as well.

More info available here: MSDN

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Comments

[Ilan]

Be careful with table names which have dots in them. RenameColumn generates a sp_rename T-SQL statement which uses uses parsename internally which has some limitations. So if you have a table name which has dots in it e.g. "SubSystemA.Tablename" then use: RenameColumn("dbo.[SubSystemA.Tablename]", "OldColumnName", "NewColumnName");

[Jess]

And just to throw in another useful tip, you can also run this in the Package Manager Console: Update-Database -Script. Then you can get the SQL sp_rename command to run at your leisure. :D

[bvj]

Preferred approach since the model's property name is also addressed. And I verified an empty migration is generated in the optional 2nd step of renaming the property.

[RasikaSam]

I think this answer assumes you have AutomaticMigration = true Then you execute command Add-Migration renameColumnXXX . After that inspect the generated migration file and delete the DropColumn and AddColum

[Chamika Sandamal]

For EF core you can use like this, migrationBuilder.RenameColumn(name: "oldname",table: "tablename",newName: "newname",schema: "schema"); docs.microsoft.com/en-us/dotnet/api/…