I've 2 tables. eg: One of these would be to store Customers and also the other would be to store Orders. Orders table that contains UserId like a foreign key. I am using Linq 2 Sql for data access procedures. I wish to place a purchase without placing a person row when the user already is available within the database.

How do i do this?

Thanks ahead of time,

Edit: This is actually the code I experience:

try
{
    context.SocialEntities.InsertOnSubmit(entity);
    context.SubmitChanges();
}
catch (Exception ex)
{
    if (ex.Message.Contains("UserUniqueness"))
    {                     
        User user = context.Users.Where(u => u.SourceUserID == entity.User.SourceUserID).FirstOrDefault();
        if (user != null)
        {
            user.SocialEntities.Add(entity);
            context.SubmitChanges();
        }
    }
}

UserUniqueness is really a unique key constraint defined within the User table for any column named SocialSourceId. Which is not primary key.

Add the brand new to the present user's Orders collection.

UPDATE:
I would recommend, you need to do the look for the consumer prior to trying to place it. I suppose, the user you attempted to include in some way is still inside your context and will get posted again next time you call SubmitChanges.