topic Re: Migrating VBA Function to vb.net in ArcObjects SDK Questions

Migrating VBA Function to vb.net

HushamHassan — Sun, 24 Nov 2013 18:09:40 GMT

Hello,
I am facing problem migrating this function from VBA to vb.net. I do appreciate your help. I am using 10.1 and vs2010

Public Function GenerateClassBreaks(pFeatLayer As IFeatureLayer, sValFieldName As String, lNClass As Long, sClassification As String) As Variant

    ' classifies data using IClassify2 and Quantile classification,
    ' then creates ClassBreaksRenderer using these breaks,
    ' and assigns to first layer in the map
    
    On Error GoTo ErrorHandler
    
    Dim pFClass As IFeatureClass
    Dim pFeature As IFeature
    Dim pFCursor As IFeatureCursor
    Dim pTable As ITable
    Dim pClassifyGEN As IClassifyGEN
    Dim pTableHistogram As ITableHistogram
    Dim pHistogram As IHistogram
    Dim frqs As Variant, xVals As Variant
    Dim i As Integer
    
    Set pFClass = pFeatLayer.FeatureClass
    Set pFCursor = pFClass.Search(Nothing, False)
    Set pFeature = pFCursor.NextFeature
    Set pTable = pFClass
    'Set pClassifyGEN = New Quantile
    Select Case sClassification
        Case "Equal Interval"
            Set pClassifyGEN = New EqualInterval
        Case "Natual Breaks"
            Set pClassifyGEN = New NaturalBreaks
        Case "Quantile"
            Set pClassifyGEN = New Quantile
        Case "Standard Deviation"
            Set pClassifyGEN = New StandardDeviation
    End Select
    'Set pClassifyGEN = New EqualInterval
    Set pTableHistogram = New TableHistogram
    Set pHistogram = pTableHistogram
    pTableHistogram.Field = sValFieldName
    
    ' matches renderer field
    Set pTableHistogram.Table = pTable
    pHistogram.GetHistogram xVals, frqs
    pClassifyGEN.Classify xVals, frqs, lNClass
    
    ' use "iNClass" number of classes
    GenerateClassBreaks = pClassifyGEN.ClassBreaks
    
    GoTo Endproc
    
ErrorHandler:
    MsgBox Err.Description, vbInformation, "GenerateClassBreaks"
    
Endproc:

    Set pFClass = Nothing
    Set pFeature = Nothing
    Set pFCursor = Nothing
    Set pTable = Nothing
    Set pClassifyGEN = Nothing
    Set pTableHistogram = Nothing
    Set pHistogram = Nothing
    
End Function

Regards

Re: Migrating VBA Function to vb.net

AlexanderGray — Mon, 25 Nov 2013 12:26:04 GMT

Perhaps you could describe your problem.

Re: Migrating VBA Function to vb.net

BruceNielsen — Sat, 11 Dec 2021 17:17:41 GMT

A couple of hints:

You no longer need to use the 'Set' keyword

You can combine the 'Dim' and 'Set' statements on one line

Dim pFClass As IFeatureClass
Set pFClass = pFeatLayer.FeatureClass

Dim pFClass As IFeatureClass = pFeatLayer.FeatureClass

Use a Try statement to trap errors. You can see the errors with ex.ToString

Re: Migrating VBA Function to vb.net

HushamHassan — Sat, 11 Dec 2021 17:17:44 GMT

agray1, bruce.nielsen
Thank you, here is my VB.net code..

Public Function GenerateClassBreaks(pFeatLayer As IFeatureLayer, sValFieldName As String, lNClass As Integer, sClassification As String) As Object
        ' classifies data using IClassify2 and Quantile classification,
        ' then creates ClassBreaksRenderer using these breaks,
        ' and assigns to first layer in the map

        Try
            Dim pFClass As IFeatureClass

            Dim pFeature As IFeature

            Dim pFCursor As IFeatureCursor

            Dim pTable As ITable

            Dim pClassifyGEN As IClassifyGEN

            Dim pTableHistogram As ITableHistogram

            Dim pHistogram As IHistogram
            Dim frqs, xVals As Object
            Dim i As Integer


            pFClass = pFeatLayer.FeatureClass

            pFCursor = pFClass.Search(Nothing, False)
            pFeature = pFCursor.NextFeature
            pTable = pFClass
            'Set pClassifyGEN = New Quantile
            Select Case sClassification
                Case "Equal Interval"
                    pClassifyGEN = New EqualInterval()
                Case "Natual Breaks"
                    pClassifyGEN = New NaturalBreaks()
                Case "Quantile"
                    pClassifyGEN = New Quantile()
                Case "Standard Deviation"
                    pClassifyGEN = New StandardDeviation()
            End Select
            'Set pClassifyGEN = New EqualInterval
            pTableHistogram = New TableHistogram()
            pHistogram = pTableHistogram
            pTableHistogram.Field = sValFieldName

            ' matches renderer field
            pTableHistogram.Table = pTable
            pHistogram.GetHistogram(xVals, frqs)
            pClassifyGEN.Classify(xVals, frqs, lNClass)

            ' use "iNClass" number of classes

            GenerateClassBreaks = pClassifyGEN.ClassBreaks
        Catch ex As Exception
            MessageBox.Show(Information.Err().Description, "GenerateClassBreaks", MessageBoxButtons.OK, MessageBoxIcon.Information)
        End Try

    End Function

but still the function doesn't return a value.

Regards

Re: Migrating VBA Function to vb.net

AlexanderGray — Mon, 25 Nov 2013 16:07:49 GMT

GenerateClassBreaks = pClassifyGEN.ClassBreaks
not sure this is the problem but, "GenerateClassBreaks = pClassifyGEN.ClassBreaks" should be:
"return pClassifyGEN.ClassBreaks"

Re: Migrating VBA Function to vb.net

HushamHassan — Sat, 11 Dec 2021 17:17:46 GMT

agray1
Thank you for your help... that not work.. the error maybe on this line of code..

Public Function GenerateClassBreaks(pFeatLayer As IFeatureLayer, sValFieldName As String, lNClass As Integer, sClassification As String) As Object

I replaced the variant with object, since there is no variant on .net

Regards

Re: Migrating VBA Function to vb.net

AlexanderGray — Tue, 26 Nov 2013 12:33:29 GMT

object is a lot like variant, that should be ok. It's not really a best practice to return an weak type in a method but not wrong. If you assign pClassifyGEN.ClassBreaks to a variable before returning it, can you check if it has a value?

Re: Migrating VBA Function to vb.net

HushamHassan — Tue, 03 Dec 2013 00:49:51 GMT

Hi agray1
Thank you and sorry for delay response, I did assign pClassifyGEN.ClassBreaks to a variable before returning it, but it has no value..
and for the same function I am getting casting error "unable to cast object of type System.double to type system.int32"

Many thanks and Regards

Re: Migrating VBA Function to vb.net

AlexanderGray — Wed, 04 Dec 2013 11:44:54 GMT

The function returns an array of doubles. If you do something like this do you get an array?

dim breaks() as double =  pClassifyGEN. pClassifyGEN.ClassBreaks

Re: Migrating VBA Function to vb.net

HushamHassan — Sat, 11 Dec 2021 17:17:49 GMT

hi,
Really apprciate your help.. still I am getting Null funciton, I did some casting as follow

Dim dataFrequency As Object = Nothing
            Dim dataValues As Object = Nothing
            Dim frqs As Integer() = TryCast(dataFrequency, Integer())
            Dim xVals As Double() = TryCast(dataValues, Double())

I am getting values for most of the variables, but still the function return Null

Regards