Question

Please have a look at the code below:

Imports System.Data.Common
Imports System.Data.SqlClient
Imports System.Data.OracleClient

Public Class clsParameterValues
    Implements IDisposable

    Private paramValues(0) As DbParameter

    Public Function AssignParameterValues(ByVal strParameterName As String, ByVal strParameterValue As String, ByVal intDatabaseType As Integer) As Integer
        Dim intArrayBound As Integer

        intArrayBound = UBound(paramValues)
        If intArrayBound > 0 Then
            ReDim paramValues(intArrayBound)
        End If

        If intDatabaseType = 1 Then

            paramValues(intArrayBound) = New SqlParameter(strParameterName, strParameterValue)
        ElseIf intDatabaseType = 2 Then
            paramValues(intArrayBound) = New OracleParameter(strParameterName, strParameterValue)
            'paramValues(intArrayBound) = New OracleParameter(":" & strParameterName, OracleType.Int32)
            'paramValues(intArrayBound).Value = strParameterValue
        End If
        Return intArrayBound
    End Function

    Public Function getParameterValues() As DbParameter()
        Return paramValues
    End Function

    Public Sub Dispose() Implements IDisposable.Dispose
        Erase paramValues
        paramValues = Nothing
    End Sub

End Class

The webpage function looks like this:

Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
            Dim objParameterValues As New clsParameterValues
                Using objParameterValues
                    'Use the objParameterValues class here.
                End Using
                objParameterValues=nothing
            End Using
End Sub

I am using IDisposable.Dispose to erase the array before setting it to Nothing. I believe this is bad practice because the Array class does not implement IDisposable. Is it even necessary to erase an array and set it to Nothing? (Does the garbage collector deal with this?)

Answer 1

Public Sub Dispose() Implements IDisposable.Dispose
    Erase paramValues
    paramValues = Nothing
End Sub

The Erase statement dates from old versions of Basic, the kind where manual memory management was useful. No more, memory management is automatic in .NET. It is still supported for compatibility reasons. All it does is set the array reference to Nothing. So your code is equivalent to:

Public Sub Dispose() Implements IDisposable.Dispose
    paramValues = Nothing
    paramValues = Nothing
End Sub

So no point to it. You should never implement IDisposible to set a variable to Nothing, that’s not the interface’s contract. A disposed object may never be used again. So no point in setting the array reference to null since that doesn’t actually do anything to the real array object on the garbage collected heap. I cannot otherwise see a scenario where you would want to help, any clsParameterValues object should have a limited lifetime. It just isn’t useful anymore when you null the array reference.

Just remove the IDisposable implementation.