Solrnet error message Object of type 'System.Collections.ArrayList' cannot be converted to type 'System.String'

Question

I am not sure if there is a bug within solrNet or I am doing something wrong. So first high level details before I jump into the detail.

What I am doing: Running a solr.Query(SearchText) command.

Error: Object of type 'System.Collections.ArrayList' cannot be converted to type 'System.String'.

Now the detail...

I am able to create documents quite happily in Solr with solr.Net and can search using

"http://localhost:8080/solr/select/?"

SolrQueryByField sq1 = SolrNet.DSL.Query.Field("flutr_EventMarketURI").Is(sfi.flutr_EventMarketURI);
SolrQuery sq2 = SolrNet.DSL.Query.Simple("flutr_EventMarketURI:\""+ sfi.flutr_EventMarketURI + "\"");
SolrQueryByField sq3 = new SolrQueryByField("flutr_EventMarketURI", sfi.flutr_EventMarketURI);

ISolrQueryResults<SolrFlutrItem> results = solr.Query(sq1); //Tried all three and same result

As you can see I am trying three ways to get an item back from the index.

Behind the scene with SolrNet it is firing off the following request to solr

Sep 19, 2012 1:08:21 PM org.apache.solr.core.SolrCore execute INFO: [] webapp=/solr path=/select/ params={q=flutr_EventMarketURI:"Football/Europe/England/Premier+League/2012/09/22/Swansea+City+-+Everton+FC/"&?=&rows=100000000} hits=1 status=0 QTime=0

This means that solr is returning the data but somewhere in the midst of doing solrNet'ty stuff this error bubbles up. - ISolrQueryResults results = solr.Query(sq1);

[ArgumentException: Object of type 'System.Collections.ArrayList' cannot be converted to type 'System.String'.]
   System.RuntimeType.TryChangeType(Object value, Binder binder, CultureInfo culture, Boolean needsSpecialCast) +4074070
   System.RuntimeType.CheckValue(Object value, Binder binder, CultureInfo culture, BindingFlags invokeAttr) +9636530
   System.Reflection.MethodBase.CheckArguments(Object[] parameters, Binder binder, BindingFlags invokeAttr, CultureInfo culture, Signature sig) +151
   System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) +223
   System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +28
   System.Reflection.RuntimePropertyInfo.SetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture) +101
   System.Reflection.RuntimePropertyInfo.SetValue(Object obj, Object value, Object[] index) +25
   SolrNet.Impl.DocumentPropertyVisitors.RegularDocumentVisitor.Visit(Object doc, String fieldName, XmlNode field) in c:\prg\SolrNet\svn\SolrNet\Impl\DocumentPropertyVisitors\RegularDocumentVisitor.cs:48
   SolrNet.Impl.DocumentPropertyVisitors.AggregateDocumentVisitor.Visit(Object doc, String fieldName, XmlNode field) in c:\prg\SolrNet\svn\SolrNet\Impl\DocumentPropertyVisitors\AggregateDocumentVisitor.cs:37
   SolrNet.Impl.DocumentPropertyVisitors.DefaultDocumentVisitor.Visit(Object doc, String fieldName, XmlNode field) in c:\prg\SolrNet\svn\SolrNet\Impl\DocumentPropertyVisitors\DefaultDocumentVisitor.cs:39
   SolrNet.Impl.SolrDocumentResponseParser`1.ParseDocument(XmlNode node, ICollection`1 fields) in c:\prg\SolrNet\svn\SolrNet\Impl\SolrDocumentResponseParser.cs:65
   SolrNet.Impl.SolrDocumentResponseParser`1.ParseResults(XmlNode parentNode) in c:\prg\SolrNet\svn\SolrNet\Impl\SolrDocumentResponseParser.cs:50
   SolrNet.Impl.ResponseParsers.ResultsResponseParser`1.Parse(XmlDocument xml, SolrQueryResults`1 results) in c:\prg\SolrNet\svn\SolrNet\Impl\ResponseParsers\ResultsResponseParser.cs:41
   SolrNet.Impl.SolrQueryResultParser`1.Parse(String r) in c:\prg\SolrNet\svn\SolrNet\Impl\SolrQueryResultParser.cs:46
   SolrNet.Impl.SolrQueryExecuter`1.Execute(ISolrQuery q, QueryOptions options) in c:\prg\SolrNet\svn\SolrNet\Impl\SolrQueryExecuter.cs:309
   SolrNet.Impl.SolrBasicServer`1.Query(ISolrQuery query, QueryOptions options) in c:\prg\SolrNet\svn\SolrNet\Impl\SolrBasicServer.cs:83
   SolrNet.Impl.SolrServer`1.Query(ISolrQuery query, QueryOptions options) in c:\prg\SolrNet\svn\SolrNet\Impl\SolrServer.cs:50
   SolrNet.Impl.SolrServer`1.Query(ISolrQuery q) in c:\prg\SolrNet\svn\SolrNet\Impl\SolrServer.cs:87
   flutrClassLibrary.TSGCsolrHelper.GetFlutrItemViaURI(String solrURL, SolrFlutrItem sfi) in D:\Dropbox\aspDevelopment\flutrBetService\flutrClassLibrary\TSGCsolrHelper.cs:89
   ReIndex.btnSendToSolr_Click(Object sender, EventArgs e) in d:\Dropbox\aspDevelopment\flutrBetService\flutrOddsAdmin\ReIndex.aspx.cs:97
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563

As a reference, here is what solr returns

"http://localhost:8080/solr/select/?q=flutr_EventMarketURI:%22Football/Europe/England/Premier+League/2012/09/22/Swansea+City+-+Everton+FC/%22&?=&rows=100000000"

<?xml version="1.0" encoding="UTF-8"?>
<response>
    <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">0</int>
        <lst name="params">
            <str name="q">flutr_EventMarketURI:"Football/Europe/England/Premier League/2012/09/22/Swansea City - Everton FC/"</str>
            <str name="?"/>
            <str name="rows">100000000</str>
        </lst>
    </lst>
    <result name="response" numFound="1" start="0">
        <doc>
            <str name="EventCategory">Football/Europe/England/Premier League</str>
            <date name="EventDate">2012-09-22T11:45:00Z</date>
            <date name="EventLastUpdated">2012-09-19T10:49:31Z</date>
            <str name="EventName">Swansea City - Everton FC</str>
            <str name="ResultsJSON">


{
  "Category_name": "Football/Europe/England/Premier League",
  "Event_name": "Everton FC - Southampton FC",
  "Event_date": "2012-09-29T14:00:00",
  "uri_event": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/",
  "Markets": [
    {
      "Market_name": "Match betting",
      "Outcomes": [
        {
          "Outcome_name": "Everton FC",
          "Odds": [
            {
              "Odds_decimal": "1.45",
              "Last_updated_date": "2012-09-19T09:49:13.9144052Z",
              "uri_odd": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/Match betting/1/odd/bwin/"
            }
          ],

          "uri_outcome": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/Match betting/1/"
        },
        {
          "Outcome_name": "Southampton FC",
          "Odds": [
            {
              "Odds_decimal": "6.45",
              "Last_updated_date": "2012-09-19T09:49:13.9144052Z",
              "uri_odd": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/Match betting/1/odd/bwin/"
            }
          ],

          "uri_outcome": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/Match betting/1/"
        },
        {
          "Outcome_name": "Draw",
          "Odds": [
            {
              "Odds_decimal": "4",
              "Last_updated_date": "2012-09-19T09:49:13.9144052Z",
              "uri_odd": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/Match betting/X/odd/bwin/"
            }
          ],
          "uri_outcome": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/Match betting/X/"
        }
      ],
      "uri_market": "Football/Europe/England/Premier League/2012/09/29/Everton FC - Southampton FC/Match betting/"
    }
  ]
}


</str>
            <str name="flutr_EventMarketURI">Football/Europe/England/Premier League/2012/09/22/Swansea City - Everton FC/</str>
            <str name="flutr_ResultType">EVENT</str>
            <arr name="text">
                <str>Football/Europe/England/Premier League/2012/09/22/Swansea City - Everton FC/</str>
                <str>Football/Europe/England/Premier League</str>
                <str>Swansea City - Everton FC</str>
                <str>Football/Europe/England/Premier League22/09/2012 11:45:00Swansea City - Everton FC1 , X , 2 , Match betting , Football/Europe/England/Premier League/2012/09/22/Swansea City - Everton FC/Match betting/ , </str>
            </arr>
        </doc>
    </result>
</response>

Here is my class

   public class SolrFlutrItem : ICloneable
    {
        public SolrFlutrItem() { }

        [SolrUniqueKey("flutr_EventMarketURI")]
        public string flutr_EventMarketURI { get; set; }

        [SolrField("flutr_ResultType")]
        public string flutr_ResultType { get; set; }

        [SolrField("EventCategory")]
        public string EventCategory { get; set; }

        [SolrField("EventDate")]
        public DateTime EventDate { get; set; }

        [SolrField("EventLastUpdated")]
        public DateTime EventLastUpdated { get; set; }

        [SolrField("EventName")]
        public string EventName { get; set; }

        [SolrField("MarketName")]
        public string MarketName { get; set; }

        [SolrField("OutcomeName")]
        public string OutcomeName { get; set; }

        [SolrField("ResultsJSON")]
        public string ResultsJSON { get; set; }

        [SolrField("InternalJSON")]
        public string InternalJSON { get; set; }

        [SolrField("text")]
        public string text { get; set; }

        public object Clone()
        {
            return this.MemberwiseClone();
        }
    }

Any ideas?

Help much appreciated.

Thanks

Answer 1

Your issue is that the text field in your SolrFlurItem class is defined as a string, yet in solr you have defined the text field as multiValued="true" which allows for multiple entries in the solr document and is shown in your solr return value. The error message is showing this mis-match because it cannot map an array of strings into a single string.

So you need to change the definition of this field to a collection like the following:

[SolrField("text")]
public ICollection<string> text { get; set; }

You can see this example and others for mapping classes to Solr results with SolrNet in the SolrNet Wiki - Mapping section.