Entity Framework 5 Multiple identity columns speci

问题:

I am creating this model as part of my code first entity framework

public class NewUserRegistration
{
    [Key]
    public int NewUserRegistrationId { get; set; }    
}

Using the Update-Database -Verbose -Force command in the Package Manger ConsoleI get this exception during the this bit of the update Applying automatic migration: 201211252223088_AutomaticMigration.

ALTER TABLE [dbo].[NewUserRegistration] ADD [NewUserRegistrationId] [int] NOT NULL IDENTITY System.Data.SqlClient.SqlException (0x80131904): Multiple identity columns specified for table 'NewUserRegistration'. Only one identity column per table is allowed. at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action1 wrapCloseInAction) at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action1 wrapCloseInAction) at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout) at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite) at System.Data.SqlClient.SqlCommand.ExecuteNonQuery() at System.Data.Entity.Migrations.DbMigrator.ExecuteSql(DbTransaction transaction, MigrationStatement migrationStatement) at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ExecuteSql(DbTransaction transaction, MigrationStatement migrationStatement) at System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable1 migrationStatements) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.ExecuteStatements(IEnumerable1 migrationStatements) at System.Data.Entity.Migrations.DbMigrator.ExecuteOperations(String migrationId, XDocument targetModel, IEnumerable1 operations, Boolean downgrading, Boolean auto) at System.Data.Entity.Migrations.DbMigrator.AutoMigrate(String migrationId, XDocument sourceModel, XDocument targetModel, Boolean downgrading) at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.AutoMigrate(String migrationId, XDocument sourceModel, XDocument targetModel, Boolean downgrading) at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable1 pendingMigrations, String targetMigrationId, String lastMigrationId)
at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable1 pendingMigrations, String targetMigrationId, String lastMigrationId)
at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration) at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.RunCore() at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run() ClientConnectionId:a39395da-5f2b-48e0-bdac-b48d75a68c68 Multiple identity columns specified for table 'NewUserRegistration'. Only one identity column per table is allowed.

There is plainly only one Identity Column specified. So why is this the case?

When I do this I get no exception.

public class NewUserRegistration
{
    [Key]
    public int Id { get; set; }    
}

Any thoughts on why this is the case?

EDIT

I should say that I am changing the name of the key. The comments say that you can't just do this. How can I drop and recreate?

Is it best to delete the database from SQL and then just run the Update-Database command again?

回答1:

I encountered the same error when trying to rename a Key column. To make the migration work, I had to reorder the order of operations in my scaffolded migration script.

Here, I made sure to order the Drop operations first, then added the new Key field afterwards.

public partial class RenameKey : DbMigration
{
    public override void Up()
    {
        DropPrimaryKey("dbo.GameSummary", new[] { "OldId" });
        DropColumn("dbo.GameSummary", "OldId");
        AddColumn("dbo.GameSummary", "Id", c => c.Int(nullable: false, identity: true));
        AddPrimaryKey("dbo.GameSummary", "Id");
    }

Hope that helps with your case.

回答2:

I also didn't have any problem simply replacing the relevant DropPrimaryKey, DropColumn, AddColumn and AddPrimaryKey commands with a RenameColumn command, e.g.

public partial class RenameKey : DbMigration
{
    public override void Up()
    {    
        RenameColumn("dbo.GameSummary", "OldId", "Id");
    }
}

回答3:

I also had a similar problem after my first migrations. What I realized was that after I deleted the database which the first migration created and then too removed the migrations folder created in my mvc application, the problem did not appear again.

回答4:

You can just change the name of the column directly from the class using something like this:

[Column("ProductID")]

Example:

namespace Z_Market.Models
{
    public  class Product
    {
        [Key, Column("ProductID")]  //This change the name of the column when you are using migration.  If you have a form created already, you have to change the connection in the for to aim the new column name.  
        public int ID { get; set; }
        public string Description { get; set; }
        public decimal Price { get; set; }
        public DateTime LastBuy { get; set; }
        public float Stock { get; set; }
        public string remarks { get; set; }
        public string deleteme { get; set; }

        public ICollection<SupplierProduct> SupplierProducts { get; set; }
    }
}

回答5:

first Add-Migration -Name then

public override void Up()
{    
    RenameColumn("dbo.Department", "OldId", "NewId");
}

回答6:

The best implementatios was:

/*Replace*/
DropPrimaryKey("dbo.GameSummary", new[] { "OldId" });
DropColumn("dbo.GameSummary", "OldId");
AddColumn("dbo.GameSummary", "Id", c => c.Int(nullable: false, identity: true));
AddPrimaryKey("dbo.GameSummary", "Id");
/*For*/
RenameColumn("dbo.GameSummary", "OldId", "Id");