title: EF Core database-first identity column issue
body: <p>I am using EF Core 3.1 with a database-first approach using Linq-to-Entities to add a new entity, but I get the following error:</p>
  
  <blockquote>
    <p>Cannot insert explicit value for identity column in table XXX when IDENTITY_INSERT is set to OFF.</p>
  </blockquote>
  
  <p>I generated the tables automatically so the ID column type is int and set by default to 0.and I cannot set it to NULL because it is not Nullable.</p>
  
  <p>I don't want to explicitly set value, I just want it to auto increase as it should.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>Person person =new Person()
  {
       FirstName="Dan",
       Age=22
  };
  db.Persons.Add(person);
  db.SaveChanges();
  </code></pre>
  
  <p>Class Person (generated from db):</p>
  
  <pre><code>public partial class Person
  {
    public int ID { get; set; }
    public string FirstName { get; set; }
    public int Age { get; set; }
  }
  </code></pre>
  
  <p>Thank in advance for any help</p>