SharePoint Client Objekt Model (CSOM) read TaxonomyField

sptax.cs

using Microsoft.SharePoint.Client;
using Microsoft.SharePoint.Client.Taxonomy;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Globalization;
using System.Linq;

namespace ICT.SharePoint.SPEvents.Events
{
    static class SPUtil
    {
        private const string ChildItems = "_Child_Items_";
        private const string ObjectType = "_ObjectType_";

        public static TaxonomyFieldValue GetTaxonomyFieldValue(this ListItem item, string internalFieldName)
        {
            if (item == null) throw new ArgumentNullException("item");
            if (internalFieldName == null) throw new ArgumentNullException("internalFieldName");

            if (!item.FieldValues.ContainsKey(internalFieldName))
            {
                throw new ArgumentException(string.Format("The field '{0}' does not exist.", internalFieldName), "internalFieldName");
            }

            var value = item[internalFieldName];
            var taxonomyFieldValue = value as TaxonomyFieldValue;
            if (taxonomyFieldValue != null)
            {
                return taxonomyFieldValue;
            }

            var dictionary = value as Dictionary<string, object>;
            if (dictionary != null)
            {
                return ConvertDictionaryToTaxonomyFieldValue(dictionary);
            }

            throw new InvalidOperationException(
                string.Format(
                    "Could not convert value of field '{0}' to a taxonomy vield value. Value is neither a TaxonomyFieldValue nor a Dictionary",
                    internalFieldName));
        }

        public static ReadOnlyCollection<TaxonomyFieldValue> GetTaxonomyFieldValueCollection(this ListItem item, string internalFieldName)
        {
            if (item == null) throw new ArgumentNullException("item");
            if (internalFieldName == null) throw new ArgumentNullException("internalFieldName");

            if (!item.FieldValues.ContainsKey(internalFieldName))
            {
                throw new ArgumentException(string.Format("The field '{0}' does not exist.", internalFieldName), "internalFieldName");
            }

            var value = item[internalFieldName];
            var taxonomyFieldValueCollection = value as TaxonomyFieldValueCollection;
            if (taxonomyFieldValueCollection != null)
            {
                return new ReadOnlyCollection<TaxonomyFieldValue>(taxonomyFieldValueCollection.ToList());
            }

            var dictionary = value as Dictionary<string, object>;
            if (dictionary != null)
            {
                return new ReadOnlyCollection<TaxonomyFieldValue>(ConvertDictionaryToTaxonomyFieldValueCollection(dictionary));
            }

            throw new InvalidOperationException(string.Format(
                "Could not convert value of field '{0}' to a taxonomy vield value. Value is neither a TaxonomyFieldValue nor a Dictionary",
                internalFieldName));
        }

        private static TaxonomyFieldValue ConvertDictionaryToTaxonomyFieldValue(Dictionary<string, object> dictionary)
        {
            if (!dictionary.ContainsKey(ObjectType) || !dictionary[ObjectType].Equals("SP.Taxonomy.TaxonomyFieldValue"))
            {
                throw new InvalidOperationException("Dictionary value represents no TaxonomyFieldValue.");
            }

            return new TaxonomyFieldValue
            {
                Label = dictionary["Label"].ToString(),
                TermGuid = dictionary["TermGuid"].ToString(),
                WssId = int.Parse(dictionary["WssId"].ToString(), CultureInfo.InvariantCulture)
            };
        }

        private static List<TaxonomyFieldValue> ConvertDictionaryToTaxonomyFieldValueCollection(Dictionary<string, object> dictionary)
        {
            if (!dictionary.ContainsKey(ObjectType) || !dictionary[ObjectType].Equals("SP.Taxonomy.TaxonomyFieldValueCollection"))
            {
                throw new InvalidOperationException("Dictionary value represents no TaxonomyFieldValueCollection.");
            }

            if (!dictionary.ContainsKey(ChildItems))
            {
                throw new InvalidOperationException(string.Format("Missing '{0}' key in TaxonomyFieldValueCollection field.", ChildItems));
            }

            var list = new List<TaxonomyFieldValue>();
            foreach (var value in (object[])dictionary[ChildItems])
            {
                var childDictionary = (Dictionary<string, object>)value;
                list.Add(ConvertDictionaryToTaxonomyFieldValue(childDictionary));
            }

            return list;
        }
    }
}