Retrieving column value from multiselect managed metadata column and updating metadat column in list.

Question

I have Library having metadata column when a document is uploaded i need update another list with metadata column of
library in list.I have an event reciever to do that,Code is given below
public override void ItemUpdated(SPItemEventProperties properties)
            base.ItemUpdated(properties);
                SPList saList = properties.Web.Lists["mylist"];
                SPListItem item = saList.AddItem();
                item["Department"] = properties.ListItem["Department"].ToString();
                EventFiringEnabled = false;
                item.Update();
                EventFiringEnabled = true;   
my elements.xml file is as below
<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <Receivers ListUrl="Documents">
      <Receiver>
        <Name>DocumentItemUpdated</Name>
        <Type> ItemUpdated</Type>
        <Assembly>$SharePoint.Project.AssemblyFullName$</Assembly>
        <Class>MyDocuments.Documents.Documents</Class>
        <SequenceNumber>10000</SequenceNumber>
      </Receiver>
  </Receivers>
</Elements>
but i did not see the the List column getting updated.But when i use the code to update a column of single line of text
it works fine.But when i do it for multi select metadata column in debug mode i could see its giving null value even though Library had column value.
Any pointers on how to update Multiselect metadata column programatically on itemeadding event in library to a list will
be helpful.

Answer 1

You need to use the TaxonomyFieldValueCollection class. The following code is from SP2010 but should still apply in SP2013. It is an example of updating multivalued taxonomy fields.
public static void SetListItemMultiMetaDataColumn(Int32 id)
using (SPSite site = new SPSite("http://basesmc2008"))
using (SPWeb web = site.OpenWeb())
TermSet termSet = null;
TaxonomySession txs = new TaxonomySession(site);
SPList list = web.Lists["Shared Documents"] as SPList;
SPListItem item = list.GetItemById(id);
TaxonomyField field = item.Fields["multimanage"] as TaxonomyField;
if (field != null)
termSet = txs.DefaultSiteCollectionTermStore.GetTermSet(field.TermSetId);
Term term = termSet.GetTerms("sts", false).FirstOrDefault();
if (field.AllowMultipleValues)
TaxonomyFieldValueCollection currentCollection = item[field.Id] as TaxonomyFieldValueCollection;
TaxonomyFieldValue tfv = new TaxonomyFieldValue(field);
tfv.TermGuid = term.Id.ToString();
tfv.Label = term.GetPath();
tfv.WssId = TaxonomyField.GetWssIdsOfTerm(site, txs.DefaultSiteCollectionTermStore.Id, termSet.Id, term.Id, false, 1).First();
currentCollection.Add(tfv);
field.SetFieldValue(item, currentCollection);
item.Update();
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