I was making a small tweak yesterday to a web part that does a CAML query against a list.  I made the change, deployed it and got hit with an error:

An unexpected error has occurred in the Three Day Outlook Weather Forecast WebPart. Please contact the system administrator. One or more field types are not installed properly. Go to the list settings page to delete these fields.

I was facing another oddball issue earlier so I didn’t immediately connect my CAML query with the error that SharePoint was reporting to me.  I did a quick bing search and and found this helpful blog post by Sandeep Nahta  (http://snahta.blogspot.com/2009/01/one-or-more-field-types-are-not.html).

Here is the bad query:

query.Query += "<Where><And><Neq><FieldRef Name=’Abbr’/><Value Type=’Text’>SFNY</Value><FieldRef Name=’Abbr’/><Value Type=’Text’>SFIS</Value></Neq></And></Where>";

Here it is fixed:

query.Query += "<Where><And><Neq><FieldRef Name=’Abbr’/><Value Type=’Text’>SFNY</Value></Neq><Neq><FieldRef Name=’Abbr’/><Value Type=’Text’>SFIS</Value></Neq></And></Where>";

So, the moral of the story is: make sure your CAML is correct or you may get an oddball error.

Subscribe to my blog.

Follow me on Twitter at http://www.twitter.com/pagalvin

</end>