Multiplicity not allowed in Entity Framework?

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3.00/5 (1 vote)

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I am making a basic data base but I am getting the following exception.

Bracelet_Guest_Source: : Multiplicity is not valid in Role 'Bracelet_Guest_Source' in relationship 'Bracelet_Guest'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be '*'.

The Models looks like:

C#

public class Bracelet
    {
        [Key]
        public int BraceletID { get; set; }

        public string BraceletNumber { get; set; }
        
        //Guest
        [ForeignKey("Guest")]
        public int GuestID { get; set; }

        public virtual  Guest Guest { get; set; }

        //Restaurant Entries
        public  virtual  RestaurantEntry RestaurantEntry { get; set; }
        
    }

 public class Guest
    {
        public Guest()
        {
            
        }

        [Key]
        public int GuestID { get; set; }

        public string FirstName { get; set; }

        public string MiddleName { get; set; }

        public string LastName { get; set; }

        public decimal Age { get; set; }

        public string Nationality { get; set; }

        public string Pin { get; set; }

        [Column(TypeName = "DateTime2")]
        public DateTime DateOfArrival { get; set; }

        [Column(TypeName = "DateTime2")]
        public DateTime DateOfDeparture { get; set; }

        public int RoomNumber { get; set; }

        public string AllInclusiveType { get; set; }

        //[ForeignKey("Bracelet")]
        //public int BraceletID { get; set; }

        public virtual Bracelet Bracelet { get; set; }
    }

 public class RestaurantEntry
    {
        private ICollection<Bracelet> bracelets; 

        public RestaurantEntry()
        {
            this.bracelets = new HashSet<Bracelet>();
        }

        [Key]
        public int RestaurantEntryID { get; set; }

        //[ForeignKey("Bracelet")]
        //public int BraceletID { get; set; }

        [Column(TypeName = "DateTime2")]
        public DateTime Time { get; set; }

        //Bracelet
        public virtual ICollection<Bracelet> Bracelets
        {
            get { return bracelets; }
            set { this.bracelets = value; }
        }
    }

The relationships are like this

Bracelet - Guest - 1 to 1
Bracelet - Restaurant Enry - 1 to many

But cant figure out what is the exception.

Posted 15-Jun-15 0:31am

Zhivko Kabaivanov

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Nathan Minier · Accepted Answer · 2015-06-15T04:11:00

This is because you have some issues in your models.

Firstly, I think you have a fundamental issue with your data model. If bracelets and Guests are 1-1, that infers that a guest can never change bracelets, which is bad design and will bite you later, should a guest need to replace their bracelet (coming back at a later date, etc.). If that's not possible in your business rules, merge the two objects by adding a BraaceletNumber property to the Guest object and using the Guest as your relationship.

Under the current code, though, you need to do this to Guest:

C#

 public class Guest
    {         
...
        // Commenting this breaks EF
        [ForeignKey("Bracelet")]
        public int BraceletID { get; set; }

        public virtual Bracelet Bracelet { get; set; }
    }

And do this to Bracelet:

C#

public class Bracelet
    {
...        
        //Guest
        [ForeignKey("Guest")]
        public int GuestID { get; set; }
 
        public virtual Guest Guest { get; set; }
 
        // This needs to be an ICollection for 1-M
        public virtual ICollection<RestaurantEntry> RestaurantEntry { get; set; }
        
    }

And do this to RestaurantEntry:

C#

public class RestaurantEntry
   {
      ...

       [ForeignKey("Bracelet")]
       public int BraceletID { get; set; }

       ...

       //Bracelet - Should be singular, each entry points to 1 bracelet
       public virtual Bracelet Bracelets { get; set; }
   }