Error : conversion from string "reference(" to type 'double' is not valid.

Question

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In the below code there is an error that shown in bold and that getfacetcount is another function in it

VB.NET

Public Function GetFacets(query As Query, facetField As [String]) As IEnumerable(Of KeyValuePair(Of [String], [String]))
    Dim ie As Integer = 0
    If Not facetsCacheContainer.ContainsKey(facetField) Then
        Dim cache As New List(Of FacetValueCache)()

        If reader Is Nothing Then
            Dim directory As Directory = FSDirectory.GetDirectory(MainWindow.folderName)
            Dim analyzer = New KeywordAnalyzer()
            Dim reader = IndexReader.Open(directory, True)
            reader = IndexReader.Open(directory, True)
            Dim parser = New QueryParser(Lucene.Net.Util.Version.LUCENE_29, facetField, analyzer)
        End If

        Dim allDistinctField = FieldCache_Fields.[DEFAULT].GetStrings(reader, facetField).Distinct()

        For Each fieldValue As String In allDistinctField
            Dim facetQuery = New TermQuery(New Term(facetField, fieldValue))
            Dim facetQueryFilter = New CachingWrapperFilter(New QueryWrapperFilter(facetQuery))
            If cache.Exists(Function(cus) cus.FacetValue = fieldValue) Then
                ie = ie + 1
            Else
                cache.Add(New FacetValueCache(fieldValue, facetQueryFilter))

            End If
        Next

        facetsCacheContainer.Add(facetField, cache)
    End If

    &#39;now calculate facets.
    Dim mainQueryFilter = New CachingWrapperFilter(New QueryWrapperFilter(query))
    Dim facetDefinition = facetsCacheContainer(facetField)

'Error here
    Return facetDefinition.Where(Function(fd) fd.GetFacetCount(reader, mainQueryFilter) &gt; 0).[Select](Function(fd) New KeyValuePair(Of [String], [String])(System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(fd.FacetValue) + "("; + fd.GetFacetCount(reader, mainQueryFilter) + ")", fd.FacetValue))
End Function

error is Conversion from string "Reference(" to type 'Double' is not valid.

What I have tried:

i have tried many sites and string but still the error is comes

Posted 18-Feb-16 22:46pm

Member 11835578

Updated 19-Feb-16 2:23am

Andy Lanng

v2

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Comments

Maciej Los 19-Feb-16 5:19am

WHat line causes the error?
Have you tried to debug your programme?

Member 11835578 19-Feb-16 5:26am

i have tried it but still error is come and the error is on

return facetDefinition.Where(Function(fd) fd.GetFacetCount(reader, mainQueryFilter) > 0).[Select](Function(fd) New KeyValuePair(Of [String], [String])(System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(fd.FacetValue) + "(" + fd.GetFacetCount(reader, mainQueryFilter) + ")", fd.FacetValue))

E.F. Nijboer 19-Feb-16 5:38am

It is no surprise that the longest and most unreadable code line is giving you problems and is almost impossible to debug... Split up to smaller code parts using well named variables and functions and you will most likely find the problem before even needing to run it again. Also, the exception message is quite clear. The value "Reference(" clearly cannot be converted to Double.

Member 11835578 19-Feb-16 5:42am

so any suggestion from you
What can i do ?

2 solutions

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Andy Lanng · Accepted Answer · 2016-02-19T00:48:00

Solution 1

It seems odd, but it's not switching fd.GetFacetCount(reader, mainQueryFilter) to a string. It's staying as a double so the '+' then switches from concatenation to addition.

Just add a tostring to make it implicit:

VB

return facetDefinition _
    .Where(Function(fd) fd.GetFacetCount(reader, mainQueryFilter) > 0) 
    .Select(Function(fd) New KeyValuePair(Of [String], [String]) 
    ( 
System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(fd.FacetValue)
+ "(" 
+ fd.GetFacetCount(reader, mainQueryFilter).ToString()
+ ")", fd.FacetValue))

Posted 19-Feb-16 0:48am

Andy Lanng

Comments

Maciej Los 19-Feb-16 7:03am

Wouldn't be better to use String.Concat() method?

Andy Lanng 19-Feb-16 7:22am

Personally I often use string.format. No idea if that's a thing in VB. There are enough syntax differences I didn't want to suggest a different way of fixing the string. I just wanted to let the OP know what was going wrong in his code ^_^

Richard Deeming 19-Feb-16 8:24am

Using + to concatenate strings in VB is decidedly odd. It's always better to use the & operator instead. See Solution #2. :)

Richard Deeming · Accepted Answer · 2016-02-19T02:23:00

In VB.NET, you can use either + or & to concatenation strings:
Concatenation Operators in Visual Basic[^]

The + operator is primarily intended for numeric addition. It has a complex set of rules that determine whether to add, concatenate, produce a compiler error, or throw a run-time exception.

The & operator always converts its operands to strings if necessary, and concatenates the strings.

VB.NET

Dim x As String = "40" + 2 ' Result: "42"
Dim y As String = "40" & 2 ' Result: "402"

Therefore, you should always use the & operator to concatenate strings.

VB.NET

Return facetDefinition.Where(Function(fd) fd.GetFacetCount(reader, mainQueryFilter) > 0).[Select](Function(fd) New KeyValuePair(Of [String], [String])(System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(fd.FacetValue) & "(" & fd.GetFacetCount(reader, mainQueryFilter) & ")", fd.FacetValue))

Error : conversion from string "reference(" to type 'double' is not valid.

2 solutions

Solution 1

Solution 2

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