序列在实体框架代码优先迁移中包含多个元素错误

Question

I created some models, added the migration and then did an update database operation, though at my last update database operation I got the error message saying:

Sequence contains more than one element

Below you can find my migration configuration:

context.Restraunts.AddOrUpdate(r => r.name,
            new Restraunt { name = "farzi", city = "a", country = "b" },
             new Restraunt { name = "prime", city = "c", country = "d" },
              new Restraunt { name = "lord", city = "e", country = "f" },
              new Restraunt
              {
                  name = "barracks",
                  city = "g",
                  country = "h",
                  Reviews = new List<RestrauntReview>{
                      new RestrauntReview{rating=5,body="good food!",reviewername="vipul"}
              }


              });

        for (int i = 0; i < 1000; i++)
        {
            context.Restraunts.AddOrUpdate(r => r.name, new Restraunt { name = i.ToString(), city = "nowhere", country = "USA" });
        }
    }
}

Below also you can find my models definitions.

public class Restraunt
{
    public int Id { get; set; }
    public string name { get; set; }
    public string city { get; set; }
    public string country { get; set; }
    public virtual ICollection<RestrauntReview> Reviews { get; set; }
}


public class RestrauntReview : IValidatableObject
{
    public int id { get; set; } 

    [Required]
    [Range(1,10)]
    public int rating { get; set; } 

    [Required]
    [StringLength(1024)]
    public string body { get; set; }

    [Display(Name="USER NAME")]
    [DisplayFormat(NullDisplayText="ANONYMOUS")]
    public string reviewername { get; set; }
    public int RestrauntID { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (rating < 2 && reviewername.ToLower().StartsWith("vipul"))
        {
            yield return new ValidationResult("sorry vipul... get out!!");
        }
    }
}

Answer 1

You have to define a Foreign Key as shown below on the RestrauntReview model.

    [ForeignKey("RestrauntID ")]
    public virtual Restraunt Restraunt { get; set; }
    public int RestrauntID { get; set; }