c# - Entity Framework 6, cannot use Ignore method on the property -

currently i'm using asp identity mvc 5.i want remove phonenumber field aspnetusers table, when use add-migration command causes following error.

you cannot use ignore method on property 'phonenumber' on type 'models.dbmodel.user' because type inherits type 'microsoft.aspnet.identity.entityframework.identityuser`

i have read tons of questions on here, of them said have ignore property in base class, however, don't have access base in case.

how can solve problem?

update: when used fluent api inside onmodelcreating method worked, don't want use way separated config class each entity.

below code:

derived entity class

public class user : identityuser     {         public  icollection<comment> comments { get; set; }      }   

config class

 public sealed class userconfig : entitytypeconfiguration<user>     {         public userconfig()         {             totable("dbo", "users");             ignore(x => x.phonenumber);             ignore(x => x.phonenumberconfirmed);         }     }   

context class

  public class websitecontext : identitydbcontext         {             public websitecontext()                 : base("xyz")             {             }              public dbset<comment> comment { get; set; }             //public dbset<user> user { get; set; }              public static websitecontext create()             {                 return new websitecontext();             }              protected override void onmodelcreating(dbmodelbuilder modelbuilder)             {                 base.onmodelcreating(modelbuilder);                 modelbuilder.configurations.add(new commentconfig());                 modelbuilder.configurations.add(new userconfig());             }         } 

try [notmapped] attribute system.componentmodel.dataannotations.schema might around limitation , has been used ignore enums in mapping, might not want