在專案中，經常會涉及列表或者文件庫之間的相互引用，而這個時候我們用的更多的就是查閱項（lookup）,以前沒有去關注取值或者賦值的問題，今天正好碰到一個Case，就順道總結一下。我們知道連結和圖片的欄位我們通過SPLinkFieldValue取值，那麼查閱項通過什麼來取值呢？答案是：SPFieldLookupValueCollection或者SPFieldLookupValue，為什麼會有兩種型別呢？起源是在新增查閱項欄位時，是否選擇了“允許多值”。一旦允許多值，就必須的通過SPFieldLookupValueCollection來做，以下是我整理的程式碼，僅供記錄：

　　1:            SPFieldLookup fieldLookup =(SPFieldLookup)list.Fields[_DisplayName];

　　2:              if (fieldLookup.GetFieldValue(item[_ColName].ToString()).GetType().Name == "SPFieldLookupValueCollection")

　　3:              {

　　4:                  SPFieldLookupValueCollection projects =

　　5:                      (SPFieldLookupValueCollection)fieldLookup.GetFieldValue(item[_ColName].ToString());

　　6:

　　7:                  foreach (SPFieldLookupValue lookupValue in projects)

　　8:                  {

　　9:                       //lookupValue.LookupValue;

　　10:                       //lookupValue.LookupId.ToString();

　　11:                  }

　　12:              }

　　13:              else

　　14:              {

　　15:                  SPFieldLookupValue projects =

　　16:                      (SPFieldLookupValue)fieldLookup.GetFieldValue(item[_ColName].ToString());

　　17:

　　18:                  //projects.LookupValue;

　　19:                  //projects.LookupId.ToString();

　　20:              }

===========================================================================================================

比如有一個 SPList 其中一列 "Depart" 為查閱項,如何對這列進行賦值

SpField field = list.Fields["Depart"];
int id = ParseLookupId(value, fieldSchemaXml);
SPFieldLookupValue fieldValue = new SPFieldLookupValue(id, value);

private int ParseLookupId(string fieldValue, string fieldMessage)
  {
  int num = 0;
  try
  {
  XmlDocument document = null;
  string fieldName = string.Empty;
  string listId = string.Empty;
  try
  {
  document = new XmlDocument();
  document.LoadXml(fieldMessage);
  listId = document.DocumentElement.Attributes["List"].Value.ToString();
  fieldName += document.DocumentElement.Attributes["ShowField"].Value.ToString();
  }
  catch (Exception er)
  {
  }
  Guid id = new Guid(listId);
  SPList list = this.Web.Lists[id];
  foreach (SPListItem item in list.Items)
  {
  try
  {
  if (item[fieldName].ToString() == fieldValue)
  {
  num = Int32.Parse(item["ID"].ToString());
  }
  }
  catch (Exception er)
  {
  }
  }
  }
  catch (Exception er)
  {
  }
  return num;
  }

====================================================================================================

 using (SPWeb web = site.OpenWeb(""))
                    {

                        SPList list = web.Lists["型別列表"];
                        web.AllowUnsafeUpdates = true;
                        foreach (SPFolder folder in list.RootFolder.SubFolders)
                        {
                            if (folder.Name == "檔名稱")
                            {
                                SPListItem item = folder.Item;

                                SPFieldLookup lookup = (SPFieldLookup)list.Fields["型別"];
                                if (lookup != null)
                                {
                                    //都不成功  直接"1;#資料夾"也不行
                                    item["型別"] = new SPFieldLookupValue(1, "資料夾");
                                    //item["型別"] =lookup.GetFieldValueAsText(new SPFieldLookupValue(1,"資料夾")) ;
                                    item.Update();//會提示只讀域  不允許更新類似的錯誤提示
                                }
                            }
                        }
                        web.AllowUnsafeUpdates = false;
                    }
=======================================================================

 SPFieldLookup lookup = (SPFieldLookup)list.Fields["Conference"];
                    if (lookup != null)
                    {
                        item["Conference"] = new SPFieldLookupValue(id, cfTitle);   //id,名字 ，即顯示出來的兩個欄位
                    }