How to set Enterprise Wiki page categories with Client Object Model

Question

In Edit mode, I can add categories to an Enterprise Wiki page by just clicking the button and entering some text. The keywords are added to the page but also to a site pool so they can be selected and reused on other pages.

Since I am migrating a Wiki with existing tags to Sharepoint, I would like to ask: how can I do the same via code, using the Client Object Model?

Basically, I want to do what they describe here: https://www.metalogix.com/help/Content%20Matrix%20Console/Blogs%20and%20Wikis%20Edition/002_HowTo/002_MigrationActions/016_MigratePageTagsAsCategories.htm

Answer 1

First retrieve the (empty) term set for the wiki category terms. This can be cached, since no-one else will be adding terms while the migration is ongoing.

        private TermSet wikiCategoryTermSet;
        const int localeId = 1033;

        private void GetWikiCategoryTermSet(ClientRuntimeContext ctx)
        {
            // Belongs to the site collection. we can cache this...
            TaxonomySession session = TaxonomySession.GetTaxonomySession(ctx);
            TermStore store = session.GetDefaultSiteCollectionTermStore();
            TermGroup group = store.Groups.GetByName("Site Collection - COMPANYNAME.sharepoint.com-sites-WIKISITENAME");

            wikiCategoryTermSet = group.TermSets.GetByName("Wiki Categories");
            ctx.Load(wikiCategoryTermSet);
            ctx.Load(wikiCategoryTermSet.Terms);
            ctx.ExecuteQuery();

        }

This code creates the terms and adds them to the common term set:

        private void CreateWikiCategoryTerms(ClientRuntimeContext ctx, string[] termNames) 
        {                      
            TermCollection terms = wikiCategoryTermSet.GetAllTerms();
            ctx.Load(terms); //ctx.Load(terms, a => a.Where(t => t.Name == termName));
            ctx.ExecuteQuery();


            foreach (var termName in termNames)
            {               
                Term term = terms.FirstOrDefault(t => t.Name == termName);
                if (term == null)
                {
                    // create                  
                    term = wikiCategoryTermSet.CreateTerm(termName, localeId, Guid.NewGuid());

                }
            }

            // commit term store changes
            wikiCategoryTermSet.TermStore.CommitAll();

            GetWikiCategoryTermSet(ctx);

        }

This method assigns the wiki categories to a page:

        public void AssignPageCategories(ClientRuntimeContext context, ListItem pageItem, string[] tagNames)
        {
            Field categoryField;
            var list = pageItem.ParentList;
            FieldCollection fields = list.Fields;

            List<Term> terms = new List<Term>();
            // get the terms corresponding to the page tags:
            foreach (var tagName in tagNames)
            {

                Term term = wikiCategoryTermSet.Terms.FirstOrDefault(t => t.Name == tagName);
                if (term == null)
                {
                    throw new Exception("Term not found.");
                }

                terms.Add(term);
            }

            // get the field that contains the category terms for this page:
            context.Load(fields, f => f.Where(fd => fd.InternalName == "Wiki_x0020_Page_x0020_Categories"));
            context.ExecuteQuery();

            categoryField = fields.FirstOrDefault();


            //make sure the TypeAsString property is loaded
            if (categoryField.IsObjectPropertyInstantiated("TypeAsString") == false)
            {
                categoryField.Context.Load(categoryField, f => f.TypeAsString);
                categoryField.Context.ExecuteQuery();
            }
            //if a multi-select managed metadata field
            if (categoryField.TypeAsString == "TaxonomyFieldTypeMulti")
            {
                //Cast Field to TaxonomyField
                TaxonomyField taxField = categoryField.Context.CastTo<TaxonomyField>(categoryField);


                string value = ""; 
                string delim = "";
                foreach (var term in terms)
                {
                    value += delim;       
                    value += $"-1;#{term.Name}|{term.Id}"; 

                    delim = ";#";
                }


                TaxonomyFieldValueCollection taxonomyFieldValueCollection = new TaxonomyFieldValueCollection(categoryField.Context, value, categoryField);

                taxField.SetFieldValueByValueCollection(pageItem, taxonomyFieldValueCollection);
            }

            pageItem.Update();
            context.ExecuteQuery();
        }