Multiplicity constraint violated VS 2010 / SQL Server / EF code-first

Question

I am new to MVC/C# and trying to work on a small project using EF code-first which includes the following 4 classes: Office, Role, User and OfficeUser.

Problem is I am trying to use same Role class between User (define master RoleId FK Role.RoleId ) and OfficeUser (define OfficeRoleId for particular office FK to Role.RoleId), Also User and OfficeUser have their own relationship.

So I am trying write my authorization using AuthorizeAttribute for which I need to get the roles of the particular user when he/she logs into the site. And when I perform a get

public User GetUserRoleByUserName(string userName, string passWord)
{
   using (var context = DataContext)
   {
      return context.Users.Include("Role")
                          .Include("OfficeUsers")
                          .SingleOrDefault(u => u.UserName == userName && u.Password == passWord);
         }
     }

I get following error

Multiplicity constraint violated. The role 'User_OfficeUsers_Target' of the relationship 'Inventory.Repository.User_OfficeUsers' has multiplicity 1 or 0..1.

Can you please tell me how can I fix this?

public class Office
{
       public Office()
       {
          OfficeUsers = new HashSet<OfficeUser>();
       }

      public int OfficeId { get; set; }
      public string OfficeName { get; set; }

      public virtual ICollection<OfficeUser> OfficeUsers { get; set; }
}

public class Role 
{
     public Role()
     {
         Users = new HashSet<User>();
         OfficeUsers = new HashSet<OfficeUser>();
     }

     public int RoleId { get; set; }
     public string RoleName { get; set; }
     public string Description { get; set; }

     public virtual ICollection<User> Users { get; set; }
     public virtual ICollection<OfficeUser> OfficeUsers { get; set; }
}

public class User
{
     public User()
     {
         OfficeUsers = new HashSet<OfficeUser>();
     }

     public int UserId { get; set; }
     public string UserName { get; set; }
     public string Password { get; set; }
     public int RoleId { get; set; }

     public virtual ICollection<OfficeUser> OfficeUsers { get; set; }
     public virtual Role Role { get; set; }
}

public class OfficeUser
{
     public OfficeUser()
     {
     }

     public int OfficeUserId { get; set; }
     public int OfficeId { get; set; }
     public int UserId { get; set; }
     [ForeignKey("Role")]
     public int OfficeRoleId { get; set; }
     public bool Active { get; set; }

     public User User { get; set; }
     public Office Office { get; set; }
     public Role Role { get; set; }
}

Answer 1

This may happen if you have not put any configuration to map the relation between User and Office. here is a sample configuration class

public class UserConfiguration : EntityTypeConfiguration<User>
    {
        public LocationConfiguration()
        {
            HasKey(a => a.Id);
            HasMany(user => user.OfficeUsers).WithOptional(officeuser => officeuser.User).
               HasForeignKey(officeuser => officeuser.UserId);
        }
    }

and add this configuration to your context as follows

public class YourContext : DbContext
    {

       // your DBSets and contructors, etc


        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new UserConfiguration());            
            base.OnModelCreating(modelBuilder);
        }


    }

EDIT

try removing the data annotation "[ForeignKey("Role")]" and then add a configuration to Role class as follows. And also add virtual keyword to Role property in OfficeUser class

public class RoleConfiguration : EntityTypeConfiguration<Role>
    {
        public LocationConfiguration()
        {
            HasKey(a => a.RoleId);
            HasMany(role =>role.OfficeUsers).WithOptional(officeuser => officeuser.Role).
               HasForeignKey(officeuser => officeuser.OfficeRoleId);
        }
    }

EDIT

declare the OfficeRoleId as

public int? OfficeRoleId { get; set; }

When you query for an OfficeUser you can use below method to use Lazy loading

YourQuery().Include(officeuser => officeuser.Role);

hope you understand the syntax Regards