Adding a managed metadata column to a list via SharePoint Server 2010 object model

Ali Mazaheri has posted a similar code recently, but since that was for content type, not list fields, and I found there are some minor difference between the two, I’ll post my solution for adding managed metadata type field to lists.

To tell the truth, I have not tried adding this kind of field to content type, but “translated” the code for handling the list fields instead, and extended with some new features.

I should note, that first I’ve tried to update the field either it was just added  or was added previously, but I’ve received a <nativehr>0x80070057</nativehr><nativestack></nativestack> error when tried to update the newly added field. Probably it was because in this case the field had its Id and InternalName properties empty yet.

1. AddTaxonomyField(SPList list, bool mayExist, String name, bool required, String description,
2.     bool addToDefaultView, bool noCrawl, String termStoreName, String groupName, String termSetName, String anchorPath,
3.     bool allowsMultiple, bool enforceUniqueValues)
4. {
5.     SPWeb web = list.ParentWeb;
6.     TaxonomySession session = new TaxonomySession(web.Site);
7.     TermStore termStore = session.TermStores[termStoreName];
8.     Group group = termStore.Groups[groupName];
9.     TermSet termSet = group.TermSets[termSetName];
10.  
11.     TaxonomyField field = null;
12.     bool fieldExists = false;
13.  
14.     // if we allow the field to exist ant it really exist
15.     // then we get the reference for the instance
16.     // it will throw an exception if the field exists
17.     // but has a different type
18.     if ((mayExist) && (list.Fields.ContainsField(name)))
19.     {
20.         field = (TaxonomyField)list.Fields[name];
21.         fieldExists = true;
22.     }
23.     // otherwise we create a new instance
24.     // it will throw an exception if the field exists
25.     // and we would like to recreate that
26.     else
27.     {
28.         field = (TaxonomyField)list.Fields.CreateNewField("TaxonomyFieldType", name);
29.     }
30.  
31.     field.Required = required;
32.     field.Description = description;
33.     field.SspId = termStore.Id;
34.     field.TermSetId = termSet.Id;
35.     field.AllowMultipleValues = allowsMultiple;
36.     field.EnforceUniqueValues = enforceUniqueValues;
37.     // field must be indexed to enfoce unique values!
38.     field.Indexed = enforceUniqueValues;
39.  
40.     if (!String.IsNullOrEmpty(anchorPath))
41.     {
42.         // see GetTermByPath method in my former post
43.         Term anchor = termSet.GetTermByPath(anchorPath);
44.         field.AnchorId = anchor.Id;
45.     }
46.  
47.     field.NoCrawl = noCrawl;
48.  
49.     if (!fieldExists)
50.     {
51.         list.Fields.Add(field);
52.     }
53.     else
54.     {
55.         field.Update();
56.     }
57.  
58.     if (addToDefaultView)
59.     {
60.         SPView view = list.DefaultView;
61.         // we add the field if it is new or if the view does not contain already it
62.         if ((!fieldExists) || (!view.ViewFields.Exists(field.InternalName)))
63.         {
64.             view.ViewFields.Add(field.Title);
65.             view.Update();
66.         }
67.     }
68.  
69.     return field;
70. }

For the GetTermByPath method I used to get the value of the AnchorId property see my former post. Anchor is a term that refers to the Term that is the starting point of the “navigation” within a TermSet. Users can select only Term that are under the anchor Term.