ASP.NET - Add Class Tags to HTML with XML Node Processing

Here is how you can process html and pick out html tags and add class attributes to them:

Imports System.Xml

    Private Function HandleClassTags(ByVal astrContent As String) As String

        Dim objxmlDoc As New XmlDocument

        Dim objNodeList_Html As XmlNodeList

        Dim strXML As String = ""

        Dim dt_ClassTags As DataTable

        Dim strResult As String = ""

        Try

            dt_ClassTags = GetClassTags() 'return datatable with one column "parent_tag" and one column as "class" ... the value for class will be assigned to the html tag in "parent_tag"

            If dt_ClassTags.Rows.Count > 0 Then

                'replace all & symbols with '---amp---'

                strXML = "<root>" & astrContent.Replace("&", "---amp---") & "</root>"

                objxmlDoc.LoadXml(strXML)

'first go through and remove the existing class set for the html tag if one exists

                For Each row As DataRow In dt_ClassTags.Rows

                    objNodeList_Html = objxmlDoc.GetElementsByTagName(row("parent_tag").ToString)

                    For Each xmlElem As System.Xml.XmlElement In objNodeList_Html

                        If xmlElem.GetAttribute("class") IsNot Nothing OrElse xmlElem.GetAttribute("class") <> "" Then

                            xmlElem.RemoveAttribute("class")

                        End If

                    Next

                Next

'now add the tags from the table as described above

                For Each row As DataRow In dt_ClassTags.Rows

                    objNodeList_Html = objxmlDoc.GetElementsByTagName(row("parent_tag").ToString)

                    For Each xmlElem As System.Xml.XmlElement In objNodeList_Html

                        If xmlElem.GetAttribute("class") Is Nothing OrElse xmlElem.GetAttribute("class") = "" Then

                            xmlElem.SetAttribute("class", row("class").ToString)

                        End If

                    Next

                Next

                strResult = objxmlDoc.OuterXml

                strResult = strResult.Replace("<root>", "").Replace("</root>", "").Replace("---amp---", "&")

            Else

                strResult = astrContent

            End If

            Return strResult

        Catch ex As Exception

            Throw ex

        Finally

            If dt_ClassTags IsNot Nothing Then

                dt_ClassTags.Dispose()

                dt_ClassTags = Nothing

            End If

            If objxmlDoc IsNot Nothing Then

                objxmlDoc = Nothing

            End If

        End Try

    End Function