asp.net - EF5 Code-First - Create new table -

i'm working asp.net mvc3 & entity framework5.

my database has been designed code-first.

entity code

public class user  {      public int id { get; set; }      public string name { get; set; }  }  public class efdbcontext : dbcontext  {     public dbset<user> users { get; set; }  } 

create db option

database.setinitializer(new dropcreatedatabaseifmodelchanges<efdbcontext>());  

i use option, database has been created.

after database has been created, need role table was.

so had modify code follows.

entity code

public class user  {      public int id { get; set; }      public string name { get; set; }  }  public class role {      public int id { get; set; }      public string name { get; set; }  }  public class efdbcontext : dbcontext  {     public dbset<user> users { get; set; }      public dbset<role> roles { get; set; } } 

i use create db option again.

in case, existing users table deleted after regeneration.

i added role table, leave data in table users.

what should do?

use code-first migrations.

database.setinitializer(null);  

then in package manager console write:

add-migration addedroles 

if did't enabled migrations before, must enable first:

enable-migrations 

and last:

update-database 

complete guid: http://msdn.microsoft.com/en-us/data/jj591621

edit

if want database upgraded automatically whenever run application, can use migratedatabasetolatestversion initializer:

database.setinitializer(new migratedatabasetolatestversion<efdbcontext, configuration>());