c# - Entity Framework Relationship Error -

i following error when using entity framework:

unable determine principal end of association between types 'xxx.domain.entities.usersettings' , 'xxx.domain.entities.user'.  principal end of association must explicitly configured using either  relationship fluent api or data annotations. 

here 2 entity classes:

public class user {     [key, column("un")]     public string username { get; set; }     public int level { get; set; }      public virtual usersettings usersettings { get; set; } }  public class usersettings {     [key]     public string username { get; set; }     public int activerefresh { get; set; }      [foreignkey("username")]     public virtual user user { get; set; } } 

i not sure how resolve error. stuck database design can't update fix issue. there way using fluent api these associations working?

a user can have usersettings object. relationship desired.

it looks need 1 zero-or-one relationship

// configure primary key user modelbuilder.entity<user>()      .haskey(t => t.username);   // map one-to-zero or 1 relationship  modelbuilder.entity<usersettings>()      .hasrequired(t => t.user)      .withoptional(t => t.usersettings); 

this not tested! remove annotations entity classes. link fluent api relationships in comment above has more examples of different kinds of relationship.