Dealing with SQLite Autoincrement column mapping in LINQtoSQL

I have folowing entity

    [Table(Name = "Users")]
    public sealed class UserDB
    {
        private Int64 _id = -1;
        private string _username = string.Empty;

        public UserDB() { }

        public UserDB(RepositoryInfo repoInfo)
        {
            UserName = repoInfo.Account;
        }

        [Column(Name = "ID", Storage = "_id",  IsDbGenerated = true, IsPrimaryKey = true, UpdateCheck = UpdateCheck.Never)]
        public Int64 ID { get { return _id; } set { _id = value; } }

        [Column(Name = "UserName", DbType="nvarchar(50)", Storage = "_username")]
        public string UserName { get { return _username; } set { _username = value; } }
    }

ID is mapped to Autoincrement INTEGER type column (actually the only type possible with autoincrement in SQLite)

When I try to add a new user to DB like this, I get an error:

public static Int64 AddUser(DataContext context, RepositoryInfo repoInfo)
{            
    UserDB udb = new UserDB(repoInfo);

    //an ID of udb is -1, but I tried different values too, doesn't change result
    var userstable = context.GetTable<UserDB>();
    userstable.InsertOnSubmit( udb );


    context.SubmitChanges(); // here I get a error, see on screen shot

    return udb.ID;

}

EDIT After a googling for and checking, seems that SQLite simply doesn't provide any SCOPE_IDENTITY() function. But Linq To SQL injects it!

How can I change this?

Actually there is no solution found by me to resolve this issue, if not that one architectural one => Change linq query to change outputted SQL.

This seems a bit hacky but according to this answer you simply need to pass "null" to your id column for sqlite to perform the autoincrement. This worked for me:

[Table(Name = "yourtable")]
class yourclass
{
    [Column(Name = "id", IsPrimaryKey=true )]
    public int? Id { get; set; }

...

Then when you create a new object for InsertOnSubmit you can just omit the id column and it will default to null.

To fetch the new id that was created using autoincrement see here