I'm working on a Sitecore upgrade from 8.2 to 10.1, which includes replacing Lucene with Solr. I have a content listing page that allows filtering by content type as well as many other fields - these are OOTB Sitecore fields, not computed. I have this SearchResultItem defined:

public class ContentTypeSearchResultItem : Sitecore.ContentSearch.SearchTypes.SearchResultItem
    public Guid Region { get; set; }

    public IEnumerable<Guid> ContentType { get; set; }


One thing I changed initially was that the names had no suffixes, so I changed "content_type" to "content_type_sm" (this was after I got the Undefined error the first time)

My fields exist in Solr:

enter image description here

and in fact in another place in the site where I pull all items with a particular template ID, when I inspect the items while debugging, I can drill into the fields and see that they have the "content_type_sm" field and it is properly populated.

But on the listing page, my query which uses this code:

var contentTypePredicate = PredicateBuilder.True<ContentTypeSearchResultItem>();
foreach (var taxonomy in taxonomies)
     contentTypePredicate = contentTypePredicate.Or(x => x.ContentType.Contains(taxonomy));
predicate = predicate.And(contentTypePredicate);

...returns no results and I see the error in my logs, ERROR Solr Error : [undefined field content_type]


Manually updating the fieldMap fixed the issue:

<field fieldName="content_type" returnType="stringCollection"></field>
  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Richard Seal
    Commented Nov 1, 2022 at 18:52

1 Answer 1


As discussed in the comments, there is no need to add the "_sm" in ContentTypeSearchResultItem.

In your latest update, it looks like you are trying to map a stringcollection to an IEnumerable < Guid >

Please can you try changing index config to:

<field fieldName="content_type" returnType="guidCollection"></field>

And then update your SearchResult to:

public IEnumerable<Guid> ContentType { get; set; }

You will need to repopulate and rebuild the index.

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