Update Manage Metadata Column

gistfile1.cs

public static void SetManagedMetaDataField(string siteUrl,
            string listName,
            string itemID,
            string fieldName,
            string term)
        {
 
            ClientContext clientContext = new ClientContext(siteUrl);
            List list = clientContext.Web.Lists.GetByTitle(listName);
            FieldCollection fields = list.Fields;
            Field field = fields.GetByInternalNameOrTitle(fieldName);
                                 
            CamlQuery camlQueryForItem = new CamlQuery();
            string queryXml = @"<view>
                                <query>
                                    <where>
                                        <eq>
                                            <fieldref name="ID">
                                            <value type="Counter">!@itemid</value>
                                        </fieldref></eq>
                                    </where>
                                </query>
                            </view>";
 
            camlQueryForItem.ViewXml = queryXml.Replace("!@itemid", itemID);
 
            ListItemCollection listItems = list.GetItems(camlQueryForItem);
 
 
            clientContext.Load(listItems, items =>; items.Include(i =>; i[fieldName]));
            clientContext.Load(fields);
            clientContext.Load(field);
            clientContext.ExecuteQuery();
            
            TaxonomyField txField = clientContext.CastTo<taxonomyfield>(field);
            string termId = GetTermIdForTerm(term, txField.TermSetId, clientContext);
 
            ListItem item = listItems[0];
                      
            TaxonomyFieldValueCollection termValues = null;
            TaxonomyFieldValue termValue = null;
 
            string termValueString = string.Empty;
 
            if (txField.AllowMultipleValues)
            {
 
                termValues = item[fieldName] as TaxonomyFieldValueCollection;
                foreach (TaxonomyFieldValue tv in termValues)
                {
                    termValueString += tv.WssId + ";#" + tv.Label + "|" + tv.TermGuid + ";#";              
                }
 
                termValueString += "-1;#" + term + "|" + termId;
                termValues = new TaxonomyFieldValueCollection(clientContext, termValueString, txField);
                txField.SetFieldValueByValueCollection(item,termValues);
                
            }
            else
            {
                termValue = new TaxonomyFieldValue();
                termValue.Label = term;
                termValue.TermGuid = termId;
                termValue.WssId = -1;
                txField.SetFieldValueByValue(item, termValue);
            }
 
            item.Update();          
            clientContext.Load(item);
            clientContext.ExecuteQuery();
        }