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
– Martin Smith, Commented Nov 1, 2013 at 13:06
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
– CodeCaster, Commented Nov 1, 2013 at 13:07
I agree with @Martin.I think something went wrong when mapping database and classes. — doganak
– doganak, Commented Nov 1, 2013 at 13:09
No @MartinSmith it's not :) I just edited it to make it more clear. — Dimo
– Dimo, Commented Nov 1, 2013 at 13:23

Dimo · Accepted Answer · 2013-11-01 13:28:22Z

40

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; }
    }

answered Nov 1, 2013 at 13:28

Dimo

3,3006 gold badges31 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

John Nguyen Over a year ago

I can not find out dll for DatabaseGenerated

Nate Barbettini Over a year ago

@JohnNguyen DatabaseGenerated and DatabaseGeneratedOption are both in the System.ComponentModel.DataAnnotations.Schema namespace, which is part of EntityFramework. Make sure you have a reference to EF or have the EF NuGet package installed.

ma11achy Over a year ago

Brilliant - thank you sir! Been trying different variations of this for 4 hours until I came across your excellent solution!

Code Monkey · Accepted Answer · 2013-11-01 13:08:31Z

2

You can configure SQL to auto-generate (and auto-increment) the primary key for the table upon inserts. Then just remove the [Key] in C# and you don't need to set the ID in the application manually, the db will generate it for you.

answered Nov 1, 2013 at 13:08

Code Monkey

6431 gold badge6 silver badges18 bronze badges

3 Comments

Code Monkey Over a year ago

Is there a specific reason why you would like to do that? From a design point of view, that is not 'generally' the norm - you can still let SQL generate a generic ID column as the pKey and set your own 'sessionID' manually as though it were a regular (non-key) column..?

Dimo Over a year ago

yes there is a specific reason :) But too difficult to get into that here in a comment :)

Code Monkey Over a year ago

Sounds like the kind of thing Dean Varillas would often do.. led me to quit.

youHaveAlsoBeenABeginner · Accepted Answer · 2020-04-17 21:51:59Z

2

I have encountered this problem multiple times while working with Microsoft SQL Server and I have followed the same way to fix it. To solve this problem, make sure Identity Specification is set to Yes. Here's how it looks like:

In this way the column number auto increments as a primary key normally would.

HOW?: right-click the table that contains the column, choose Design, select the primary key and in Column Properties window find Identity Specification and set it to Yes.

answered Apr 17, 2020 at 21:51

youHaveAlsoBeenABeginner

3314 silver badges17 bronze badges

Collectives™ on Stack Overflow

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

3 Answers 3

3 Comments

3 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related