SPFieldLookupValue

//得到查阅项的值
SPWeb web = site.OpenWeb();
SPList list = web.Lists["DemoList"];
SPListItem item = list.GetItemById(itemId);
SPFieldLookupValue objLookupFieldValue = new SPFieldLookupValue(item["lookup"].ToString());

//可以得到以下属性
objLookupFieldValue.LookupValue        //得到查阅项的值
objLookupFieldValue.LookupId          //得到或设置查阅项ID

//也可以利用itemID得到查阅项集合
SPFieldLookupValueCollection objLookupFieldValueCol = new              SPFieldLookupValueCollection(item["lookup"].ToString());

for (int i = 0; i < objLookupFieldValueCol.Count; i++)
{
SPFieldLookupValue singlevalue = objLookupFieldValueCol[i];
}