IDENTITY_INSERT设置为OFF时，无法手动为标识插入ID实体插入显式值

Question

I have a table Worker :

 public class Worker
 {
        public int ID { get; set; }
        public string Firstname { get; set; }
        public string Lastname { get; set; }
        public string Fathername { get; set; }
        public string email { get; set; }
        public string Company_name { get; set; }    
}  

I try to add a new worker:

new Worker { Firstname = "John", Lastname = "Rambo", Fathername = "First_Blood", email = "Rocky@hh.ru", Company_name = "Survive" },

And I get error in application insights from last debug

Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.

System.Data.SqlClient.SqlException: Cannot insert explicit value for identity column in table 'Worker' when IDENTITY_INSERT is set to OFF.

at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1

Of course I can remove ID and it added automatically. But I want to add it manually of if it is nulled then generate automatically.

Answer 1

Firstly, your ID column will never be null as you are using the int type and not the nullable int type.

You can make your int type nullable by changing public int ID { get; set; } public int ID { get; set; } public int ID { get; set; } to public int? ID { get; set; } public int? ID { get; set; }

The reason you are receiving this error is because IDENTITY_INSERT is set to off on your database.

If you apply the following attribute/convention to the property in your class and update the changes to the database you should find you are allowed to insert into the identity column.

public class Worker
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int ID { get; set; }
    public string Firstname { get; set; }
    public string Lastname { get; set; }
    public string Fathername { get; set; }
    public string email { get; set; }
    public string Company_name { get; set; }    
} 

Alternatively, you can use the OnModelCreating overload as such;

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Worker>().Property(x => x.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
}