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, Nov 01 '13 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](http://stackoverflow.com/questions/4999853/using-entity-framework-code-first-ctp5-how-do-i-create-a-primary-key-column-tha) — CodeCaster, Nov 01 '13 at 13:07
I agree with @Martin.I think something went wrong when mapping database and classes. — doganak, Nov 01 '13 at 13:09
No @MartinSmith it's not :) I just edited it to make it more clear. — Dimo, Nov 01 '13 at 13:23

score 38 · Accepted Answer · answered Nov 01 '13 at 13:28

38

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 01 '13 at 13:28

Dimo

3,158
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I can not find out dll for DatabaseGenerated – John Nguyen Aug 18 '14 at 03:53
@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. – Nate Barbettini Dec 19 '14 at 15:02
Brilliant - thank you sir! Been trying different variations of this for 4 hours until I came across your excellent solution! – ma11achy May 08 '15 at 14:38

score 2 · Answer 2 · answered Nov 01 '13 at 13:08

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 01 '13 at 13:08

Code Monkey

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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..? – Code Monkey Nov 01 '13 at 13:28
yes there is a specific reason :) But too difficult to get into that here in a comment :) – Dimo Nov 01 '13 at 13:33
1

Sounds like the kind of thing Dean Varillas would often do.. led me to quit. – Code Monkey Sep 08 '15 at 00:03

score 1 · Answer 3 · answered Apr 17 '20 at 21:51

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.

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

3 Answers3

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