Cannot insert the value NULL into column in ASP.NET MVC Entity Framework

Question

When trying to use this code:

var model = new MasterEntities();

var customer = new Customers();
customer.Sessionid = 25641;

model.Customers.Add(customer);
model.SaveChanges();

I get:

{"Cannot insert the value NULL into column 'Sessionid', table 'master.dbo.Column'; column does not allow nulls. INSERT fails.\r\nThe statement has been terminated."}

The column "Sessionid" is actually the primary key and is marked with [KEY] like this:

 public class Customers
    {   
        [Key]
        public long Sessionid { get; set; }
        public long? Pers { get; set; }
    }

So according to this question, it seems as if when the property is marked with [KEY], EF ignores my own declaration of Sessionid since it expects the database to assign the value.

So how can I solve this? If I remove [KEY] I get the "entity type has no key defined" exception...

Is your table actually called Column? And in the master database? — Martin Smith
possible duplicate of Using Entity Framework Code First CTP5, how do I create a primary key column that are INTs and are not identity columns — CodeCaster
I agree with @Martin.I think something went wrong when mapping database and classes. — doganak
No @MartinSmith it's not :) I just edited it to make it more clear. — Dimo

Dimo Dimo · Accepted Answer · 2013-11-01T13:28:22

I solved it by adding [DatabaseGenerated(DatabaseGeneratedOption.None)] like this:

public class Customers
    {   
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public long Sessionid { get; set; }
        public long? Pers { get; set; }
    }

Cannot insert the value NULL into column in ASP.NET MVC Entity Framework

3 Answers