how i can search my Term Store inside my Event Reciever based on the term Label

Question

I am working on an event receiver inside sharepoint server 2013. the event receiver will fire when a user added a new item inside a custom list. Now i am trying to do the following :-

1- get the current item title using properties.ListItem.Title;

2- search the term store based on the item title.

3- create a new wiki page, add for the wiki category column to assign it the term i retrieved on step-2.

now i have the following code:-

public override void ItemAdded(SPItemEventProperties properties)
 {
base.ItemAdded(properties);

    PublishingSite pSite = new PublishingSite(properties.Site);
    SPContentType ctype = pSite.ContentTypes["Enterprise Wiki Page"];
    PageLayoutCollection pageLayouts = pSite.GetPageLayouts(ctype, true);
    PageLayout pageLayout = pageLayouts["EnterpriseWiki.aspx"];
    PublishingWeb pWeb = PublishingWeb.GetPublishingWeb(properties.Web);
    PublishingPageCollection pPages = pWeb.GetPublishingPages();
    PublishingPage pPage = pPages.Add(newPageName+".aspx", pageLayout);
    newpage["Wiki_x0020_Page_x0020_Categories"] = properties.ListItem.Title.Trim();

now i was not expecting my above code to work, as i am trying to assign a string to a managed property column. so i got this error:-

The given guid does not exist in the term store

so can anyone advice how i can search the term store and get the related term which is equal to the properties.ListItem.Title and then assign the term to the newpage["Wiki_x0020_Page_x0020_Categories"] column ?

Answer 1

Try either of the below 2 approaches, should work:

Approach 1:

SPList oList = oWebsiteRoot.Lists[listName];  //get the list name
TaxonomySession session = new TaxonomySession(properties.Site); //pass spsite object
TaxonomyField oField = oList.Fields["Wiki_x0020_Page_x0020_Categories"] as TaxonomyField; //pass internal name of column
TermSet oSet = session.DefaultSiteCollectionTermStore.GetTermSet(oField.TermSetId);
TermCollection oColl = oSet.Terms;
foreach (Term oTerm in termColl)
{
    if (oTerm.Name == properties.ListItem.Title)
    {
        TaxonomyField taxonomyField = oList.Fields["Wiki_x0020_Page_x0020_Categories"]as TaxonomyField;
        TaxonomyFieldValue taxonomyFieldValue = new TaxonomyFieldValue(taxonomyField);
        taxonomyFieldValue.TermGuid = oTerm.Id.ToString();
        taxonomyFieldValue.Label = oTerm.Name;

        newpage["Wiki_x0020_Page_x0020_Categories"] = taxonomyFieldValue;
        item.Update(); //splistitem update
        oList.Update(); //probably not necessary
        break;
    }
}

Approach 2: Traverse the term store

string listName = "CustomList";
string fieldName = "Wiki_x0020_Page_x0020_Categories";
SPList oList = oWebsiteRoot.Lists[listName];  //pass the splist 
TaxonomyField oField = (TaxonomyField)oList.Fields[fieldName];

// Get a TaxonomySession from the site
TaxonomySession session = new TaxonomySession(properties.Site);
TermStore termStore = null;
// Get a TermStore from the session
if (session.TermStores != null)
{
    termStore = session.TermStores[oField.SspId];
}

foreach(Group g in termStore.Groups)
{
    TermSet termSet = g.TermSets.FirstOrDefault(t => t.Id == oField.TermSetId);

    if (termSet != null)
    {
        Term term = termSet.Terms[properties.ListItem.Title]);      
        TaxonomyFieldValue taxonomyFieldValue = new TaxonomyFieldValue(oField);
        taxonomyFieldValue.TermGuid = term.Id.ToString();
        taxonomyFieldValue.Label = term.Name;
        newpage["Wiki_x0020_Page_x0020_Categories"] = taxonomyFieldValue;
        item.Update();  //splistitem update
        oList.Update();  //probably not necessary
        break;
    }
}

Answer 2

EDIT: This is an answer for using CSOM, not SSOM, which is what the code sample in the question uses.

Dealing with taxonomy terms is much more complicated than it seems on the surface. To get a term efficiently so you don't have to iterate over the whole taxonomy store, you need to know the term group name and the term set name. Here is a handy helper function, which I use to get a term by title. Provide properties.ListItem.Title for the termName argument.

public static Term GetTerm(ClientRuntimeContext ctx, string groupName, string termSetName, string termName)
    {
        TaxonomySession session = TaxonomySession.GetTaxonomySession(ctx);
        TermStore store = session.GetDefaultSiteCollectionTermStore();
        TermGroup group = store.Groups.GetByName(groupName);
        TermSet termSet = group.TermSets.GetByName(termSetName);
        TermCollection terms = termSet.GetAllTerms();
        ctx.Load(terms, a => a.Where(t => t.Name == termName));
        ctx.ExecuteQuery();
        Term term = terms.FirstOrDefault();
        return term;
    }

If the above function returns null, than it cannot find a term by that name in that term set. Once you get the term, setting the value of the Wiki_x0020_Page_x0020_Categories field using that term can be tricky. Interestingly, there are many ways to set a TaxonomyField value, but I demonstrate one below that I have used previously.

public void SetTaxonomyFieldValue(Field taxonomyField, Term term, ListItem item)
    {
        //make sure the TypeAsString property is loaded
        if (taxonomyField.IsObjectPropertyInstantiated("TypeAsString") == false)
        {
            taxonomyField.Context.Load(taxonomyField, f => f.TypeAsString);
            taxonomyField.Context.ExecuteQuery();
        }
        //if a multi-select managed metadata field
        if (taxonomyField.TypeAsString == "TaxonomyFieldTypeMulti")
        {
            //Cast Field to TaxonomyField
            TaxonomyField taxField = (TaxonomyField)taxonomyField;
            //create a value string for the field value. You cannot use TaxonomyField.SetFieldValueByTerm since Term.Context != Field.Context
            string strValue = string.Format("-1;#{0}|{1}",term.Name,term.Id);
            TaxonomyFieldValueCollection taxonomyFieldValueCollection = new TaxonomyFieldValueCollection(taxonomyField.Context, strValue, taxonomyField);
            taxField.SetFieldValueByValueCollection(item, taxonomyFieldValueCollection);
        }
    }