Public Function ExecuteReader(ByVal behavior As 
Microsoft.ReportingServices.DataProcessing.CommandBehavior) As 
Microsoft.ReportingServices.DataProcessing.IDataReader Implements 
Microsoft.ReportingServices.DataProcessing.IDbCommand.ExecuteReader
            Try
                'This function is the heart of our custom implementation.
                GetEstimatedCostAndRows(Me.CommandText)

                'Does the total Cost exceed the Max Cost or Estimated Rows?
                If m_MaxEstimatedCost > 0 Then
                    If m_SubmittedEstimatedCost > m_MaxEstimatedCost Then
                        Throw New Exception("This query exceeds the Maximum Cost Value")
                    End If
                End If
                If m_MaxEstimatedRows > 0 Then
                    If m_SubmittedEstimatedRows > m_MaxEstimatedRows Then
                        Throw New Exception("This query exceeds the Maximum Estimated Row Value")
                    End If
                End If

                Return m_innerDBComm.ExecuteReader(behavior)
            Catch ex As Exception
                Throw ex
            End Try
        End Function

….
‘ Begin Callout A
Private Sub GetEstimatedCostAndRows(ByVal sCommandText As String)
            Try
                Dim oSQLDR As IDataReader = Nothing
                m_SubmittedEstimatedRows = 0
                m_SubmittedEstimatedCost = 0

                'Set Showplan_xml on
                m_innerDBCommCostEstimate.CommandType = 
Microsoft.ReportingServices.DataProcessing.CommandType.Text
                m_innerDBCommCostEstimate.CommandText = "set showplan_xml on"
                oSQLDR = m_innerDBCommCostEstimate.ExecuteReader(CommandBehavior.SingleResult)
                oSQLDR.Dispose()

                'Build the Query that is going to be executed.  We need to account for Parameters - which we
                ' will do so by declaring them as Variants
                Dim sCommandTextParams As String = String.Empty
                If Not m_innerDBComm.Parameters Is Nothing Then
                    For Each oIDParam As IDataParameter In m_innerDBComm.Parameters
                        sCommandTextParams = sCommandTextParams & "DECLARE " & 
oIDParam.ParameterName & " SQL_VARIANT; "
                    Next
                End If

                m_innerDBCommCostEstimate.CommandText = sCommandTextParams & sCommandText

                Dim sXMLPlan As String = String.Empty
                oSQLDR = m_innerDBCommCostEstimate.ExecuteReader(CommandBehavior.SingleResult)
                While oSQLDR.Read
                    sXMLPlan = sXMLPlan & oSQLDR.GetValue(0).ToString
                End While
                oSQLDR.Dispose()

                m_innerDBCommCostEstimate.CommandText = "set showplan_xml off"
                oSQLDR = m_innerDBCommCostEstimate.ExecuteReader(CommandBehavior.SingleResult) 
'Turns XML Showplan off
                oSQLDR.Dispose()

                Console.WriteLine(sXMLPlan)

                'Parse the XML to get the Estimated Total Cost and Rows for the query
                Dim strReader As New StringReader(sXMLPlan)
                Dim xreader As New System.Xml.XmlTextReader(strReader)
                Dim doc As New XPathDocument(xreader, XmlSpace.Preserve)
                Dim navigator As System.Xml.XPath.XPathNavigator = doc.CreateNavigator()
                Dim nsmgr As New XmlNamespaceManager(navigator.NameTable)
                'The exact namespace will depend on the showplan's version - we'll just grab it from
                '   the string representation of the sXMLPlan
                Dim sNameSpace As String = Me.GetXMLSchemaNamespace(sXMLPlan)
                nsmgr.AddNamespace("sql", sNameSpace)

                Dim xpression As XPathExpression = _
                    navigator.Compile("//sql:Batch/sql:Statements/sql:StmtSimple/@StatementSubTreeCost")

                xpression.SetContext(nsmgr)
                Dim iterator As XPathNodeIterator = navigator.Select(xpression)
                Dim val As String = String.Empty
                ' sum costs of all query plans in this batch
                While iterator.MoveNext
                    m_SubmittedEstimatedCost = m_SubmittedEstimatedCost + CType(iterator.Current.Value, 
Single)
                End While
                'Does the total Cost exceed the Max Cost
                If m_MaxEstimatedCost > 0 Then
                    If m_SubmittedEstimatedCost > m_MaxEstimatedCost Then
                        Return
                    End If
                End If


                ' get estimated row count - StatementEstRows
                xpression = 
navigator.Compile("//sql:Batch/sql:Statements/sql:StmtSimple/@StatementEstRows")
                xpression.SetContext(nsmgr)
                iterator = navigator.Select(xpression)
                ' sum costs of all query plans in this batch
                While iterator.MoveNext
                    m_SubmittedEstimatedRows = m_SubmittedEstimatedRows + 
CType(iterator.Current.Value, Integer)
                End While
                'Does the estimated row count exceed the Max Row Count
                If m_MaxEstimatedRows > 0 Then
                    If m_SubmittedEstimatedRows > m_MaxEstimatedRows Then
                        Return
                    End If
                End If


            Catch ex As Exception
                'Some queries may not return showplan values
                'e.g. - http://msdn2.microsoft.com/en-us/library/ms187886.aspx
                m_SubmittedEstimatedRows = 0
                m_SubmittedEstimatedCost = 0
            Finally
                m_innerDBCommCostEstimate.Dispose()
            End Try
        End Sub
‘ End Callout A


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