Entity Framework The ALTER TABLE statement conflicted with the FOREIGN KEY constraint

Question

On updating database in Entity Framework , Code first Migration, I am getting this error:

The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Clients_dbo.MedicalGroups_MedicalGroupId". The conflict occurred in database "hrbc", table "dbo.MedicalGroups", column 'Id'.

This is my class:

public partial class Client {     [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]     public int Id { get; set; }      public string FirstName { get; set; }     public string LastName { get; set; }     public int? MedicalGroupId { get; set; }     [ForeignKey("MedicalGroupId")]     public virtual MedicalGroups MedicalGroup { get { return _MedicalGroup; } set { _MedicalGroup = value; } } } 

Here is my 2nd class:

public partial class MedicalGroups {     [Key]     public int Id { get; set; }     public string Name { get; set; } } 

And this is my migration which I am trying to apply:

public override void Up() {     AddForeignKey("dbo.Clients", "MedicalGroupId", "dbo.MedicalGroups", "Id");     CreateIndex("dbo.Clients", "MedicalGroupId"); } 

Answer 1

Check that there is not existing data in the database that is conflicting with the FK constraint causing the creation to fail.