' Copyright 2012 ESRI
' 
' All rights reserved under the copyright laws of the United States
' and applicable international laws, treaties, and conventions.
' 
' You may freely redistribute and use this sample code, with or
' without modification, provided you include the original copyright
' notice and use restrictions.
' 
' See the use restrictions.
' 

Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Runtime.InteropServices
Imports ESRI.ArcGIS.DataSourcesRaster
Imports ESRI.ArcGIS.esriSystem
Imports ESRI.ArcGIS.Geodatabase
Imports ESRI.ArcGIS.Geometry
Imports ESRI.ArcGIS.ADF.CATIDs

Namespace CustomFunction
  <Guid("652642F3-9106-4EB3-9262-A4C39E03BC56")> _
  <ClassInterface(ClassInterfaceType.None)> _
  <ProgId("CustomFunction.NDVICustomFunction")> _
  <ComVisible(True)> _
  Public Class NDVICustomFunction
    Implements IRasterFunction
    Implements IPersistVariant
    Implements IDocumentVersionSupportGEN
    Implements IXMLSerialize
    Implements IXMLVersionSupport
    #Region "Private Members"
    Private myUID As UID
    ' UID for the Function.
    Private myRasterInfo As IRasterInfo
    ' Raster Info for the Function
    Private myPixeltype As rstPixelType
    ' Pixel Type of the Function.
    Private myName As String
    ' Name of the Function.
    Private myDescription As String
    ' Description of the Function.
    Private myValidFlag As Boolean
    ' Flag to specify validity of the Function.
    Private myFunctionHelper As IRasterFunctionHelper
    ' Raster Function Helper object.
    Private myInpPixeltype As rstPixelType
    Private myInpNumBands As Integer

    Private myBandIndices As String()
    #End Region

    Public Sub New()
      myName = "NDVI Custom Function"
      myPixeltype = rstPixelType.PT_FLOAT
      myDescription = "Custom NDVI Function which calculates the NDVI without any scaling."
      myValidFlag = True
      myFunctionHelper = New RasterFunctionHelperClass()

      myInpPixeltype = myPixeltype
      myInpNumBands = 0

      myBandIndices = Nothing

      myUID = New UIDClass()
      myUID.Value = "{652642F3-9106-4EB3-9262-A4C39E03BC56}"
    End Sub

    #Region "IRasterFunction Members"

    ''' <summary>
    ''' Name of the Raster Function.
    ''' </summary>
    Public Property Name() As String Implements IRasterFunction.Name
      Get
        Return myName
      End Get
      Set
        myName = value
      End Set
    End Property

    ''' <summary>
    ''' Pixel Type of the Raster Function
    ''' </summary>
    Public Property PixelType() As rstPixelType Implements IRasterFunction.PixelType
      Get
        Return myPixeltype
      End Get
      Set
        myPixeltype = value
      End Set
    End Property

    ''' <summary>
    ''' Output Raster Info for the Raster Function
    ''' </summary>
    Public ReadOnly Property RasterInfo() As IRasterInfo Implements IRasterFunction.RasterInfo
      Get
        Return myRasterInfo
      End Get
    End Property

    ''' <summary>
    ''' Description of the Raster Function
    ''' </summary>
    Public Property Description() As String Implements IRasterFunction.Description
      Get
        Return myDescription
      End Get
      Set
        myDescription = value
      End Set
    End Property

    ''' <summary>
    ''' Initialize the Raster function using the argument object. This is one of the two
    ''' main functions to implement for a custom Raster function. The raster object is 
    ''' dereferenced if required and given to the RasterFuntionHelper object to bind.
    ''' </summary>
    ''' <param name="pArguments">Arguments object used for initialization</param>
    Public Sub Bind(pArguments As Object) Implements IRasterFunction.Bind
      Try
        ' Check if the Arguments object is of the correct type.
        Dim customFunctionArgs As INDVICustomFunctionArguments = Nothing
        If TypeOf pArguments Is INDVICustomFunctionArguments Then
          customFunctionArgs = DirectCast(pArguments, INDVICustomFunctionArguments)
          Dim inputRaster As Object = customFunctionArgs.Raster
          If TypeOf customFunctionArgs.Raster Is IRasterFunctionVariable Then
            Dim rasterFunctionVariable As IRasterFunctionVariable = DirectCast(customFunctionArgs.Raster, IRasterFunctionVariable)
            inputRaster = rasterFunctionVariable.Value
          End If

          ' Call the Bind method of the Raster Function Helper object.
          myFunctionHelper.Bind(inputRaster)
        Else
          ' Throw an error if incorrect arguments object is passed.
          Throw New System.Exception("Incorrect arguments object. Expected: INDVICustomFunctionArguments")
        End If

        ' Check to see if Band Indices exist.
        If customFunctionArgs.BandIndices IsNot Nothing AndAlso customFunctionArgs.BandIndices <> "" Then
          myBandIndices = customFunctionArgs.BandIndices.Split(" "C)
        Else
          ' If not, throw an error.
          Throw New System.Exception("Incorrect parameters specified. Expected: Valid band indices.")
        End If

        ' Create a new RasterInfo object and initialize from the FunctionHelper object.
        ' A new RasterInfo Object is created because assigning myFunctionHelper.RasterInfo
        ' directly creates a reference.
        myRasterInfo = New RasterInfoClass()
        myRasterInfo.BandCount = myFunctionHelper.RasterInfo.BandCount
        myRasterInfo.BlockHeight = myFunctionHelper.RasterInfo.BlockHeight
        myRasterInfo.BlockWidth = myFunctionHelper.RasterInfo.BlockWidth
        myRasterInfo.CellSize = myFunctionHelper.RasterInfo.CellSize
        myRasterInfo.Extent = myFunctionHelper.RasterInfo.Extent
        myRasterInfo.FirstPyramidLevel = myFunctionHelper.RasterInfo.FirstPyramidLevel
        myRasterInfo.Format = myFunctionHelper.RasterInfo.Format
        myRasterInfo.GeodataXform = myFunctionHelper.RasterInfo.GeodataXform
        myRasterInfo.MaximumPyramidLevel = myFunctionHelper.RasterInfo.MaximumPyramidLevel
        myRasterInfo.NativeExtent = myFunctionHelper.RasterInfo.NativeExtent
        myRasterInfo.NativeSpatialReference = myFunctionHelper.RasterInfo.NativeSpatialReference
        myRasterInfo.NoData = myFunctionHelper.RasterInfo.NoData
        myRasterInfo.Origin = myFunctionHelper.RasterInfo.Origin
        myRasterInfo.PixelType = rstPixelType.PT_FLOAT
        ' Output pixel type should be output of the NDVI.
        myRasterInfo.Resampling = myFunctionHelper.RasterInfo.Resampling
        myRasterInfo.SupportBandSelection = myFunctionHelper.RasterInfo.SupportBandSelection

        ' Store required input properties.
        myInpPixeltype = myRasterInfo.PixelType
        myInpNumBands = myRasterInfo.BandCount

        ' Set output pixel properties.
        myRasterInfo.BandCount = 1
        myPixeltype = rstPixelType.PT_FLOAT

        ' Perform validation to see if the indices passed are valid.
        If myInpNumBands < 2 OrElse myBandIndices.Length < 2 Then
          ' If not, throw an error.
          Throw New System.Exception("Incorrect parameters specified. Expected: Valid band indices.")
        End If
        For i As Integer = 0 To myBandIndices.Length - 1
          Dim currBand As Integer = Convert.ToInt16(myBandIndices(i)) - 1
          If (currBand < 0) OrElse (currBand > myInpNumBands) Then
            ' If not, throw an error.
            Throw New System.Exception("Incorrect parameters specified. Expected: Valid band indices.")
          End If
        Next
      Catch exc As Exception
        Dim myExc As New System.Exception("Exception caught in Bind method: " & exc.Message, exc)
        Throw myExc
      End Try
    End Sub

    ''' <summary>
    ''' Read pixels from the input Raster and fill the PixelBlock provided with processed pixels.
    ''' </summary>
    ''' <param name="pTlc">Point to start the reading from in the Raster</param>
    ''' <param name="pRaster">Reference Raster for the PixelBlock</param>
    ''' <param name="pPixelBlock">PixelBlock to be filled in</param>
    Public Sub Read(pTlc As IPnt, pRaster As IRaster, pPixelBlock As IPixelBlock) Implements IRasterFunction.Read
      Try
        ' Create a new pixel block to read the input data into.
        ' This is done because the pPixelBlock represents the output
        ' pixel block which is different from the input. 
        Dim pBHeight As Integer = pPixelBlock.Height
        Dim pBWidth As Integer = pPixelBlock.Width
        Dim pBlockSize As IPnt = New PntClass()
        pBlockSize.X = pBWidth
        pBlockSize.Y = pBHeight
        Dim inputPixelBlock As IPixelBlock = New PixelBlockClass()
        DirectCast(inputPixelBlock, IPixelBlock4).Create(myInpNumBands, pBWidth, pBHeight, myInpPixeltype)

        ' Call Read method of the Raster Function Helper object to read the input pixels into
        ' the inputPixelBlock.
        myFunctionHelper.Read(pTlc, Nothing, pRaster, inputPixelBlock)

        Dim inpPixelValues1 As System.Array
        Dim inpPixelValues2 As System.Array
        Dim outPixelValues As System.Array
        Dim index1 As Integer = Convert.ToInt16(myBandIndices(0)) - 1
        

        ' Get NIR band index specified by user.
        Dim index2 As Integer = Convert.ToInt16(myBandIndices(1)) - 1
        

        ' Get Red Band index specified by user.
        ' Get the correct bands from the input.
        Dim ipPixelBlock As IPixelBlock3 = DirectCast(inputPixelBlock, IPixelBlock3)
                inpPixelValues1 = DirectCast(ipPixelBlock.PixelData(index1), System.Array)
                inpPixelValues2 = DirectCast(ipPixelBlock.PixelData(index2), System.Array)
                outPixelValues = DirectCast(DirectCast(pPixelBlock, IPixelBlock3).PixelData(0), System.Array)
        Dim i As Integer = 0
        Dim k As Integer = 0
        Dim pixelValue As Double = 0.0
        Dim nirValue As Double = 0.0
        Dim irValue As Double = 0.0
        ' Perform the NDVI computation and store the result in the output pixel block.
        For i = 0 To pBHeight - 1
          For k = 0 To pBWidth - 1
            nirValue = Convert.ToDouble(inpPixelValues1.GetValue(k, i))
            irValue = Convert.ToDouble(inpPixelValues2.GetValue(k, i))
            ' Check if input is not NoData.
            If (Convert.ToByte(ipPixelBlock.GetNoDataMaskVal(index1, k, i)) = 1) AndAlso Convert.ToByte(ipPixelBlock.GetNoDataMaskVal(index2, k, i)) = 1 Then
              ' NDVI[k] = (NIR[k]-Red[k])/(NIR[k]+Red[k]);
              If (nirValue + irValue) <> 0 Then
                ' Check for division by 0.
                pixelValue = (nirValue - irValue) / (nirValue + irValue)
                If pixelValue < -1.0 OrElse pixelValue > 1.0 Then
                  pixelValue = 0.0
                End If
              Else
                pixelValue = 0.0
              End If
            End If
            outPixelValues.SetValue(CSng(pixelValue), k, i)
          Next
        Next
        ' Set the output pixel values on the output pixel block.
                DirectCast(pPixelBlock, IPixelBlock3).PixelData(0) = outPixelValues
        ' Copy over the NoData mask from the input and set it on the output.
                DirectCast(pPixelBlock, IPixelBlock3).NoDataMask(0) = DirectCast(inputPixelBlock, IPixelBlock3).NoDataMask(0)
      Catch exc As Exception
        Dim myExc As New System.Exception("Exception caught in Read method: " & exc.Message, exc)
        Throw myExc
      End Try
    End Sub

    ''' <summary>
    ''' Update the Raster Function
    ''' </summary>
    Public Sub Update() Implements IRasterFunction.Update
      Try
      Catch exc As Exception
        Dim myExc As New System.Exception("Exception caught in Update method: ", exc)
        Throw myExc
      End Try
    End Sub

    ''' <summary>
    ''' Property that specifies whether the Raster Function is still valid.
    ''' </summary>
    Public ReadOnly Property Valid() As Boolean Implements IRasterFunction.Valid
      Get
        Return myValidFlag
      End Get
    End Property

    #End Region

    #Region "IPersistVariant Members"

    ''' <summary>
    ''' UID to identify the function.
    ''' </summary>
    Public ReadOnly Property ID() As UID Implements IPersistVariant.ID
      Get
        Return myUID
      End Get
    End Property

    ''' <summary>
    ''' Load the properties of the function from the stream provided
    ''' </summary>
    ''' <param name="Stream">Stream that contains the serialized form of the function</param>
    Public Sub Load(Stream As IVariantStream) Implements IPersistVariant.Load
      If TypeOf Stream Is IDocumentVersion Then
        Dim docVersion As IDocumentVersion = DirectCast(Stream, IDocumentVersion)
        If docVersion.DocumentVersion >= esriArcGISVersion.esriArcGISVersion10 Then
          Dim streamVersion As esriArcGISVersion = CType(CInt(Stream.Read()), esriArcGISVersion)
          If streamVersion >= esriArcGISVersion.esriArcGISVersion10 Then
            myName = DirectCast(Stream.Read(), String)
            myDescription = DirectCast(Stream.Read(), String)
            myPixeltype = CType(CInt(Stream.Read()), rstPixelType)
          End If
        End If
      End If
    End Sub

    ''' <summary>
    ''' Save the properties of the function to the stream provided
    ''' </summary>
    ''' <param name="Stream">Stream to which to serialize the function into</param>
    Public Sub Save(Stream As IVariantStream) Implements IPersistVariant.Save
      If TypeOf Stream Is IDocumentVersion Then
        Dim docVersion As IDocumentVersion = DirectCast(Stream, IDocumentVersion)
        If docVersion.DocumentVersion >= esriArcGISVersion.esriArcGISVersion10 Then
          Stream.Write(CInt(esriArcGISVersion.esriArcGISVersion10))
          Stream.Write(myName)
          Stream.Write(myDescription)
          Stream.Write(CInt(myPixeltype))
        End If
      End If
    End Sub

    #End Region

    #Region "IDocumentVersionSupportGEN Members"

    ''' <summary>
    ''' Convert the instance into an object supported by the given version
    ''' </summary>
    ''' <param name="docVersion">Version to convert to</param>
    ''' <returns>Object that supports given version</returns>
    Public Function ConvertToSupportedObject(docVersion As esriArcGISVersion) As Object Implements IDocumentVersionSupportGEN.ConvertToSupportedObject
      Return Nothing
    End Function

    ''' <summary>
    ''' Check if the object is supported at the given version
    ''' </summary>
    ''' <param name="docVersion">Version to check against</param>
    ''' <returns>True if the object is supported</returns>
    Public Function IsSupportedAtVersion(docVersion As esriArcGISVersion) As Boolean Implements IDocumentVersionSupportGEN.IsSupportedAtVersion
      If docVersion >= esriArcGISVersion.esriArcGISVersion10 Then
        Return True
      Else
        Return False
      End If
    End Function

    #End Region

    #Region "IXMLSerialize Members"

    ''' <summary>
    ''' Deserialize the Raster Function from the datastream provided
    ''' </summary>
    ''' <param name="data">Xml stream to deserialize the function from</param>
    Public Sub Deserialize(data As IXMLSerializeData) Implements IXMLSerialize.Deserialize
      myName = data.GetString(data.Find("Name"))
      myDescription = data.GetString(data.Find("Description"))
      myPixeltype = CType(data.GetInteger(data.Find("PixelType")), rstPixelType)
    End Sub

    ''' <summary>
    ''' Serialize the Raster Function into the stream provided.
    ''' </summary>
    ''' <param name="data">Xml stream to serialize the function into</param>
    Public Sub Serialize(data As IXMLSerializeData) Implements IXMLSerialize.Serialize
      data.TypeName = "NDVICustomFunction"
      data.TypeNamespaceURI = "http://www.esri.com/schemas/ArcGIS/10.1"
      data.AddString("Name", myName)
      data.AddString("Description", myDescription)
      data.AddInteger("PixelType", CInt(myPixeltype))
    End Sub

    #End Region

    #Region "IXMLVersionSupport Members"

    ''' <summary>
    ''' Returns the namespaces supported by the object
    ''' </summary>
    Public ReadOnly Property MinNamespaceSupported() As String Implements IXMLVersionSupport.MinNamespaceSupported
      Get
        Return "http://www.esri.com/schemas/ArcGIS/10.1"
      End Get
    End Property

    #End Region

    #Region "COM Registration Function(s)"
    <ComRegisterFunction> _
    Private Shared Sub Reg(regKey As String)
      ESRI.ArcGIS.ADF.CATIDs.RasterFunctions.Register(regKey)
    End Sub

    <ComUnregisterFunction> _
    Private Shared Sub Unreg(regKey As String)
      ESRI.ArcGIS.ADF.CATIDs.RasterFunctions.Unregister(regKey)
    End Sub
    #End Region
  End Class

  <Guid("157ACDCC-9F2B-4CC4-BFFD-FEB933F3E788")> _
  <InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)> _
  Public Interface INDVICustomFunctionArguments
    Inherits IRasterFunctionArguments
    Inherits IPersistVariant
    Inherits IDocumentVersionSupportGEN
    Inherits IXMLSerialize
    Inherits IXMLVersionSupport
    #Region "INDVICustomFunctionArguments Members"

    <DispId(&H50505001)> _
    Property Raster() As Object

    <DispId(&H50505002)> _
    Property BandIndices() As String
    #End Region
  End Interface

  <Guid("CB684500-0A15-46C5-B1C1-8062A1629F66")> _
  <ClassInterface(ClassInterfaceType.None)> _
  <ProgId("CustomFunction.NDVICustomFunctionArguments")> _
  <ComVisible(True)> _
  Public Class NDVICustomFunctionArguments
    Implements INDVICustomFunctionArguments
    #Region "Private Members"
    Private myName As String
    Private myDescription As String

    Private myUID As UID
    ' UID for the NDVI Custom Function Arguments.
    Private myProperties As IPropertySet
    ' Property set to store the properties of the arguments object.
    #End Region
    Public Sub New()
      myName = "NDVI Custom Function Arguments"
      myDescription = "Arguments object for the NDVI Custom Function"

      ' Set default values
      myProperties = New PropertySetClass()
      myProperties.SetProperty("Raster", Nothing)
      myProperties.SetProperty("BandIndices", "1 2")
      ' Default value for band indexes: first two bands of image.
      myUID = New UIDClass()
      myUID.Value = "{CB684500-0A15-46C5-B1C1-8062A1629F66}"
    End Sub

    #Region "NDVICustomFunctionArguments Members"

    ''' <summary>
    ''' Raster to apply the raster function to.
    ''' </summary>
    Public Property Raster() As Object Implements INDVICustomFunctionArguments.Raster
      Get
        Return GetDereferencedValue("Raster")
      End Get
      Set
        myProperties.SetProperty("Raster", value)
      End Set
    End Property

    ''' <summary>
    ''' Indices of the bands to use in the NDVI computation.
    ''' </summary>
    Public Property BandIndices() As String Implements INDVICustomFunctionArguments.BandIndices
      Get
                Return Convert.ToString(GetDereferencedValue("BandIndices"))
      End Get
      Set
        myProperties.SetProperty("BandIndices", value)
      End Set
    End Property

    ''' <summary>
    ''' Dereference and return the value of the property whose name is given if necessary.
    ''' </summary>
    ''' <param name="name">Name of the property to check.</param>
    ''' <returns>Dereferenced value of the property corresponding to the name given.</returns>
    Private Function GetDereferencedValue(name As String) As Object
      Dim value As Object = myProperties.GetProperty(name)
      If value IsNot Nothing AndAlso TypeOf value Is IRasterFunctionVariable AndAlso Not (TypeOf value Is IRasterFunctionTemplate) Then
                Dim rFVar As IRasterFunctionVariable = DirectCast(value, IRasterFunctionVariable)
                Return rFVar.Value
      End If
      Return value
    End Function

    #End Region

    #Region "IRasterFunctionArguments Members"

    ''' <summary>
    ''' A list of files associated with the raster
    ''' </summary>
    Public ReadOnly Property FileList() As IStringArray Implements IRasterFunctionArguments.FileList
      Get
        Dim rasterObject As Object = myProperties.GetProperty("Raster")
        Dim rasterDataset As IRasterDataset = Nothing
        If TypeOf rasterObject Is IRasterDataset Then
          rasterDataset = DirectCast(rasterObject, IRasterDataset)
        ElseIf TypeOf rasterObject Is IName Then
          rasterDataset = DirectCast(DirectCast(rasterObject, IName).Open(), IRasterDataset)
        End If
        If rasterDataset IsNot Nothing AndAlso TypeOf rasterDataset Is IRasterDatasetInfo Then
          Dim rasterDatasetInfo As IRasterDatasetInfo = DirectCast(rasterDataset, IRasterDatasetInfo)
          Return rasterDatasetInfo.FileList
        Else
          Return Nothing
        End If
      End Get
    End Property

    ''' <summary>
    ''' Get the value associated with the name provided.
    ''' </summary>
    ''' <param name="Name">Name of the property</param>
    ''' <returns>Value of the property name provided</returns>
    Public Function GetValue(Name As String) As Object Implements IRasterFunctionArguments.GetValue
      Return myProperties.GetProperty(Name)
    End Function

    ''' <summary>
    ''' A list of all the names in the property set.
    ''' </summary>
    Public ReadOnly Property Names() As IStringArray Implements IRasterFunctionArguments.Names
      Get
        ' Generate a list of names in the propertyset.
        Dim names__1 As Object = Nothing, values As Object = Nothing
        myProperties.GetAllProperties(names__1, values)
        Dim myNames As IStringArray = New StrArray()
        Dim nameArray As String() = DirectCast(names__1, String())
        For i As Integer = 0 To nameArray.GetLength(0) - 1
          myNames.Add(nameArray(i))
        Next
        Return myNames
      End Get
    End Property

    ''' <summary>
    ''' Set the given property name to the given value
    ''' </summary>
    ''' <param name="Name">Name of the property</param>
    ''' <param name="Value">Value of the property</param>
    Public Sub PutValue(Name As String, Value As Object) Implements IRasterFunctionArguments.PutValue
      myProperties.SetProperty(Name, Value)
    End Sub

    ''' <summary>
    ''' Remove the value of the property name provided
    ''' </summary>
    ''' <param name="Name">Name of the property to be removed</param>
    Public Sub Remove(Name As String) Implements IRasterFunctionArguments.Remove
      myProperties.RemoveProperty(Name)
    End Sub

    ''' <summary>
    ''' Clear the property set of all names and values.
    ''' </summary>
    Public Sub RemoveAll() Implements IRasterFunctionArguments.RemoveAll
      myProperties = Nothing
      myProperties = New PropertySetClass()
    End Sub

    ''' <summary>
    ''' A list of all the values in the property set
    ''' </summary>
    Public ReadOnly Property Values() As IVariantArray Implements IRasterFunctionArguments.Values
      Get
        ' Generate a list of values in the propertyset.
        Dim names As Object = Nothing, values__1 As Object = Nothing
        myProperties.GetAllProperties(names, values__1)
        Dim myValues As IVariantArray = New VarArray()
        Dim valArray As Object() = DirectCast(values__1, Object())
        For i As Integer = 0 To valArray.GetLength(0) - 1
          myValues.Add(valArray(i))
        Next
        Return myValues
      End Get
    End Property

    ''' <summary>
    ''' Resolve variables containing field names with the corresponding values.
    ''' </summary>
    ''' <param name="pRow">The row corresponding to the function raster dataset.</param>
    ''' <param name="pPropertySet">Property Set to add the list of the names and the resolved values to.</param>
    Public Sub Resolve(pRow As IRow, pPropertySet As IPropertySet) Implements IRasterFunctionArguments.Resolve
      ResolveRasterVal(pRow)
    End Sub

    ''' <summary>
    ''' Update the variables containing field names to their updated values.
    ''' </summary>
    ''' <param name="pRow">The row corresponding to the function raster dataset.</param>
    ''' <param name="pPropertySet">Property Set to add the list of the names and the updated values to.</param>
    ''' <param name="pTemplateArguments">The arguements object containing the properties to update if</param>
    Public Sub Update(pRow As IRow, pPropertySet As IPropertySet, pTemplateArguments As IRasterFunctionArguments) Implements IRasterFunctionArguments.Update
      Resolve(pRow, pPropertySet)
    End Sub

    ''' <summary>
    ''' Resolve the 'Raster' variable if it contains field names with the corresponding values.
    ''' </summary>
    ''' <param name="pRow">The row corresponding to the function raster dataset.</param>
    Private Sub ResolveRasterVal(pRow As IRow)
      Try
        ' Get the Raster property.
        Dim myRasterObject As Object = myProperties.GetProperty("Raster")
        ' Check to see if it is a variable
        If TypeOf myRasterObject Is IRasterFunctionVariable Then
          Dim rasterVar As IRasterFunctionVariable = DirectCast(myRasterObject, IRasterFunctionVariable)
          Dim rasterVal As Object = FindPropertyInRow(rasterVar, pRow)
          If rasterVal IsNot Nothing AndAlso TypeOf rasterVal Is String Then
            Dim datasetPath As String = DirectCast(rasterVal, String)
            rasterVar.Value = OpenRasterDataset(datasetPath)
          End If
        End If
      Catch exc As Exception
        Dim myExc As New System.Exception("Exception caught in ResolveRasterVal: " & exc.Message, exc)
        Throw myExc
      End Try
    End Sub

    ''' <summary>
    ''' Check the Name and Alias properties of the given Raster Function Variable to see
    ''' if they contain a field name and get the value of the corresponding field if needed.
    ''' </summary>
    ''' <param name="rasterFunctionVar">The Raster Function Variable to check.</param>
    ''' <param name="pRow">The row corresponding to the function raster dataset.</param>
    ''' <returns></returns>
    Private Function FindPropertyInRow(rasterFunctionVar As IRasterFunctionVariable, pRow As IRow) As Object
      Dim varName As String = ""
      Dim varNames As IStringArray = New StrArrayClass()
      varName = rasterFunctionVar.Name
      ' If the name of  the variable contains '@Field'
      If varName.Contains("@Field.") Then
        varNames.Add(varName)
      End If
      ' Add it to the list of names.
      ' Check the aliases of the variable
      For i As Integer = 0 To rasterFunctionVar.Aliases.Count - 1
        ' Check the list of aliases for the '@Field' string
                varName = rasterFunctionVar.Aliases.Element(i)
        If varName.Contains("@Field.") Then
          varNames.Add(varName)
          ' and add any that are found to the list of names.
        End If
      Next

      ' Use the list of names and find the value by looking up the appropriate field.
      For i As Integer = 0 To varNames.Count - 1
        ' Get the variable name containing the field string
                varName = varNames.Element(i)
        ' Replace the '@Field' with nothing to get just the name of the field.
        Dim fieldName As String = varName.Replace("@Field.", "")
        Dim rowFields As IFields = pRow.Fields
        ' Look up the index of the field name in the row.
        Dim fieldIndex As Integer = rowFields.FindField(fieldName)
        ' If it is a valid index and the field type is string, return the value.
                If fieldIndex <> -1 AndAlso ((rowFields.Field(fieldIndex)).Type = esriFieldType.esriFieldTypeString) Then
                    Return pRow.Value(fieldIndex)
                End If
      Next
      ' If no value has been returned yet, return null.
      Return Nothing
    End Function

    ''' <summary>
    ''' Open the Raster Dataset given the path to the file.
    ''' </summary>
    ''' <param name="path">Path to the Raster Dataset file.</param>
    ''' <returns>The opened Raster Dataset.</returns>
    Private Function OpenRasterDataset(path As String) As IRasterDataset
      Try
        Dim inputWorkspace As String = System.IO.Path.GetDirectoryName(path)
        Dim inputDatasetName As String = System.IO.Path.GetFileName(path)
        Dim factoryType As Type = Type.GetTypeFromProgID("esriDataSourcesRaster.RasterWorkspaceFactory")
        Dim workspaceFactory As IWorkspaceFactory = DirectCast(Activator.CreateInstance(factoryType), IWorkspaceFactory)
        Dim workspace As IWorkspace = workspaceFactory.OpenFromFile(inputWorkspace, 0)
        Dim rasterWorkspace As IRasterWorkspace = DirectCast(workspace, IRasterWorkspace)
        Dim myRasterDataset As IRasterDataset = rasterWorkspace.OpenRasterDataset(inputDatasetName)
        Return myRasterDataset
      Catch exc As Exception
        Throw exc
      End Try
    End Function
    #End Region

    #Region "IPersistVariant Members"

    ''' <summary>
    ''' UID to identify the object.
    ''' </summary>
    Public ReadOnly Property ID() As UID Implements IPersistVariant.ID
      Get
        Return myUID
      End Get
    End Property

    ''' <summary>
    ''' Load the properties of the argument object from the stream provided
    ''' </summary>
    ''' <param name="Stream">Stream that contains the serialized form of the argument object</param>
    Public Sub Load(Stream As IVariantStream) Implements IPersistVariant.Load
      If TypeOf Stream Is IDocumentVersion Then
        Dim docVersion As IDocumentVersion = DirectCast(Stream, IDocumentVersion)
        If docVersion.DocumentVersion >= esriArcGISVersion.esriArcGISVersion10 Then
          Dim streamVersion As esriArcGISVersion = CType(CInt(Stream.Read()), esriArcGISVersion)
          If streamVersion >= esriArcGISVersion.esriArcGISVersion10 Then
            myName = DirectCast(Stream.Read(), String)
            myDescription = DirectCast(Stream.Read(), String)
            myProperties = DirectCast(Stream.Read(), IPropertySet)
          End If
        End If
      End If
    End Sub

    ''' <summary>
    ''' Save the properties of the argument object to the stream provided
    ''' </summary>
    ''' <param name="Stream">Stream to which to serialize the argument object into</param>
    Public Sub Save(Stream As IVariantStream) Implements IPersistVariant.Save
      If TypeOf Stream Is IDocumentVersion Then
        Dim docVersion As IDocumentVersion = DirectCast(Stream, IDocumentVersion)
        If docVersion.DocumentVersion >= esriArcGISVersion.esriArcGISVersion10 Then
          Dim names As Object = Nothing, values As Object = Nothing
          myProperties.GetAllProperties(names, values)
          Dim nameArray As String() = DirectCast(names, String())
          Dim valArray As Object() = DirectCast(values, Object())
          For i As Integer = 0 To nameArray.GetLength(0) - 1
            If TypeOf valArray(i) Is IDataset Then
              Dim myDatasetName As IName = DirectCast(valArray(i), IDataset).FullName
              myProperties.SetProperty(nameArray(i), myDatasetName)
            End If
          Next
          Stream.Write(CInt(esriArcGISVersion.esriArcGISVersion10))
          Stream.Write(myName)
          Stream.Write(myDescription)
          Stream.Write(myProperties)
        End If
      End If
    End Sub

    #End Region

    #Region "IDocumentVersionSupportGEN Members"

    ''' <summary>
    ''' Convert the instance into an object supported by the given version
    ''' </summary>
    ''' <param name="docVersion">Version to convert to</param>
    ''' <returns>Object that supports given version</returns>
    Public Function ConvertToSupportedObject(docVersion As esriArcGISVersion) As Object Implements IDocumentVersionSupportGEN.ConvertToSupportedObject
      Return Nothing
    End Function

    ''' <summary>
    ''' Check if the object is supported at the given version
    ''' </summary>
    ''' <param name="docVersion">Version to check against</param>
    ''' <returns>True if the object is supported</returns>
    Public Function IsSupportedAtVersion(docVersion As esriArcGISVersion) As Boolean Implements IDocumentVersionSupportGEN.IsSupportedAtVersion
      If docVersion >= esriArcGISVersion.esriArcGISVersion10 Then
        Return True
      Else
        Return False
      End If
    End Function

    #End Region

    #Region "IXMLSerialize Members"

    ''' <summary>
    ''' Deserialize the argument object from the datastream provided
    ''' </summary>
    ''' <param name="data">Xml stream to deserialize the argument object from</param>
    Public Sub Deserialize(data As IXMLSerializeData) Implements IXMLSerialize.Deserialize
      Dim nameIndex As Integer = data.Find("Names")
      Dim valIndex As Integer = data.Find("Values")
      If nameIndex <> -1 AndAlso valIndex <> -1 Then
        Dim myNames As IStringArray = DirectCast(data.GetVariant(nameIndex), IStringArray)
        Dim myValues As IVariantArray = DirectCast(data.GetVariant(valIndex), IVariantArray)
        For i As Integer = 0 To myNames.Count - 1
                    myProperties.SetProperty(myNames.Element(i), myValues.Element(i))
        Next
      End If
    End Sub

    ''' <summary>
    ''' Serialize the argument object into the stream provided.
    ''' </summary>
    ''' <param name="data">Xml stream to serialize the argument object into</param>
    Public Sub Serialize(data As IXMLSerializeData) Implements IXMLSerialize.Serialize
      '#Region "Prepare PropertySet"
      Dim names As Object = Nothing, values As Object = Nothing
      myProperties.GetAllProperties(names, values)
      Dim myNames As IStringArray = New StrArray()
      Dim nameArray As String() = DirectCast(names, String())
      Dim myValues As IVariantArray = New VarArray()
      Dim valArray As Object() = DirectCast(values, Object())
      For i As Integer = 0 To nameArray.GetLength(0) - 1
        myNames.Add(nameArray(i))
        If TypeOf valArray(i) Is IDataset Then
          Dim myDatasetName As IName = DirectCast(valArray(i), IDataset).FullName
          myValues.Add(myDatasetName)
        Else
          myValues.Add(valArray(i))
        End If
      Next
      '#End Region
      data.TypeName = "NDVICustomFunctionArguments"
      data.TypeNamespaceURI = "http://www.esri.com/schemas/ArcGIS/10.1"
      data.AddObject("Names", myNames)
      data.AddObject("Values", myValues)
    End Sub

    #End Region

    #Region "IXMLVersionSupport Members"

    ''' <summary>
    ''' Returns the namespaces supported by the object
    ''' </summary>
    Public ReadOnly Property MinNamespaceSupported() As String Implements IXMLVersionSupport.MinNamespaceSupported
      Get
        Return "http://www.esri.com/schemas/ArcGIS/10.1"
      End Get
    End Property

    #End Region
  End Class
End Namespace