try
{
	using (var db = new dbContext())
	{
		// Create new stub with correct id and attach to context.
		var entity = new myEntity { PageID = pageid };
		db.Pages.Attach(entity);

		// Now the entity is being tracked by EF, update required properties.
		entity.Title = "new title";
		entity.Url = "new-url";
		
		// EF knows only to update the propeties specified above.
		db.SaveChanges();
	}
}
catch (DataException)
{
	// process exception
}