Question

This is my MVC model:

public class Link
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid ID { get; set; }

    [DisplayName("Shorted URL")]
    public string SURL { get; set; }

    [DisplayName("General Link")]
    public string OriginalURL { get; set; }

    [DisplayName("Click Count")]
    public int ClickCount { get; set; }
}

and this is LinkDBContext class:

public class LinkDBContext : DbContext
{
    public DbSet<Link> Links { get; set; }
}

when I want to add some data to database using this code:

    private string GetNewID(string url, string id)
    {
        LinkDBContext Links = new LinkDBContext();
        //id = "http://" + id;
        List<Link> link = Links.Links.Where(a => (a.OriginalURL == id && a.SURL == id)).ToList();
        if (link.Count == 0)
        {
            List<Link> LLinks = Links.Links.ToList<Link>();
            Link li = new Link();
            //li.ID = new Guid();
            li.ClickCount = 0;
            li.SURL = id;
            li.OriginalURL = url;
            Links.Links.Add(li);
            Links.SaveChanges();
            Links.Dispose();
            return id.ToString();
        }

        return GetNewID(url);
    }

I just get an exception that is: Cannot insert the value NULL into column 'ID', table 'GhiasiDB.dbo.Links'; column does not allow nulls. INSERT fails.The statement has been terminated.

what is the problem and how can I resolve it?

---

update

I changed the type of ID from Guid to int and when I tried again I got this exception from List<Link> LLinks = Links.Links.ToList<Link>(); of GetNewID method:The 'ID' property on 'Link' could not be set to a 'Guid' value. You must set this property to a non-null value of type 'Int32'.
and I don’t know where did it come from. I changed all Guides to int!

Answer 1

If you allowed EF to generate the tables it would create the PK with a default value set to (newid()). You can set it manually if you designed the database first.