将实体附加到数据上下文

Question

In LINQ to SQL, is it possible to check to see if an entity is already part of the data context before trying to attach it?

A little context if it helps...

I have this code in my global.asax as a helper method. Normally, between requests, this isn't a problem. But right after signing in, this is getting called more than once, and the second time I end up trying to attach the Member object in the same unit of work where it was created.

private void CheckCurrentUser()
{
    if (!HttpContext.Current.User.Identity.IsAuthenticated)
    {
        AppHelper.CurrentMember = null;
        return;
    }

    IUserService userService = new UserService();

    if (AppHelper.CurrentMember != null)
        userService.AttachExisting(AppHelper.CurrentMember);
    else
        AppHelper.CurrentMember = userService.GetMember(
            HttpContext.Current.User.Identity.Name,
            AppHelper.CurrentLocation);
}

Answer 1

I believe there are two methods to do this.

DataContext.TableName.Contains(Item)

or we use the id field. If the item is inserted in the Database, then it will be assigned a row.

if(Item.id == 0)
   DataContext.Insert(Item)
else
   DataContext.Update(Item)

Answer 2

Rather than attaching to a new data context why not just requery the object in the new datacontext? It believe it is a more reliable and stateless strategy.