Sharepoint TaxonomyField Object

Question

How do you get a TaxonomyField object from the Managed Property Title? Does anyone know a good article/tutorial on programatically working with taxonomies in Sharepoint 2010?

Answer 1

Creating a TaxonomyField goes something like this:

var site = SPContext.Current.Site;
var web = site.RootWeb;
var taxonomySession = new TaxonomySession(site);
var termStore = taxonomySession.TermStores[0];
var termGroup = termStore.Groups["My Group"];
var termSet = termGroup.TermSets["My TermSet"];

var taxonomyField = web.Fields.CreateNewField("TaxonomyFieldType", "My Tag Field") as TaxonomyField;
taxonomyField.SspId = termStore.Id;
taxonomyField.TermSetId = termSet.Id;
taxonomyField.AllowMultipleValues = true;
web.Fields.Add(taxonomyField);
web.Update();

If you're going to work with Managed Metadata the Andrew Connell's article series is almost a must.

To get a reference to the field just use:

var taxonomyField = web.Fields["My Tag Field"] as TaxonomyField;

To set the value in a list item ALWAY use one of the TaxonomyField.SetFieldValue overloads, NEVER just use item["My Tag Field"] = xxx. The TaxonomyField is implemented as a lookup into a hidden list and the term needs to be copied into this list when first used.

If you need to get an exising field based on TermSet name the you have to loop through the fields to find it:

var site = SPContext.Current.Site;
var web = site.RootWeb;
var taxonomySession = new TaxonomySession(site);
var termStore = taxonomySession.TermStores[0];
var termGroup = termStore.Groups["My Group"];
var termSet = termGroup.TermSets["My TermSet"];

foreach (var field in web.Fields)
{
  var taxonomyField = field as TaxonomyField;
  if (taxonomyField != null
   && taxonomyField.SspId == termStore.Id
   && taxonomyField.TermSetId == termSet.Id)
  {
     // here taxonomyField is the wanted field
  }
}

Answer 2

Try this:

using System;
using System.Linq;
using System.Collections.Generic;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Taxonomy;


class Program
{
    static void Main(string[] args)
    {
        //Your site url
        string siteUrl = "http://spsite";

        using (SPSite site = new SPSite(siteUrl))
        using (SPWeb web = site.OpenWeb())
        {
            //metadata field name
            string mmField = "MetaDataField";
            //List name
            string listName = "Shared Documents";
            SPList list = web.Lists[listName];
            foreach (SPListItem item in list.Items)
            {
                TaxonomyFieldValue value =  item[mmField] as TaxonomyFieldValue;
                if (value != null)
                {
                    Console.WriteLine(value.Label);
                }
            }
        }   
    }
}