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

Question

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

Can I rename a table column without automatically deleting data?

Answer 1

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

Answer 2

As already mentioned, replace AddColumn and DropColumn , which are automatically generated using 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"); } } } 

Answer 3

Now this answer is based on my knowledge of EF4.3, so I hope that migrations work approximately the same in EF5 :) After you have created the migration, you should be able to add code to the Up and Down methods, between discarding the old property and creating new property. This code should move the property data in the right direction. I solved this with the SQL () method, in which you can enter the original SQL to move the data.

In the Up method of the migration method:

 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 can link your code to the database that you are currently working with (since you are writing raw database-specific SQL code). There may be other methods available for moving data.

Additional information is available here: MSDN

Answer 4

Adding the answer to Josh Gallagher:

In some places, sp_RENAME syntax is described as follows:

 sp_RENAME 'TableName.[OldColumnName]' , '[NewColumnName]', 'COLUMN' 

However, in reality this will include brackets in the new column name.

The DbMigration RenameColumn () method is likely to do the same, so avoid using parentheses when specifying the name of a new column.

In addition, automatically generated commands in Up () and Down () include DropPrimaryKey () and AddPrimaryKey () if the renamed column is part of the primary key. They are not needed when using RenameColumn (). The primary sp_RENAME automatically updates the primary key, if necessary.

Answer 5

You can get a redirect 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 the DB column to be the same, you can rename the property later and remove the Column attribute.

Answer 6

you have 2 steps to rename the column in the first code migration

• In the first step, you add a ColumnAttribute above the column that has been changed, and then the update-database command

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

2. Second step

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

   • add here up and down

RenameColumn ("name" "yourDatabase", "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 be linked through name_column in the database and name_type using the property method in the model above.

Answer 7

like + Josh Gallagher said you can use up () to do things like:

 public override void Up() { RenameColumn("dbo.atable","odlanem","newname"); AddColumn("dbo.anothertable", "columname", c => c.String(maxLength: 250)); } 

I found this good help in gettin for migration;)