XML schema validation - Line number always returns 0

I am validating and XML file against a Schema using the following code.

Public Sub LoadXml(xmlFilePath As String, xsdFilePath As String)
    Dim doc As New XmlDocument()
    doc.Load(xmlFilePath)
    doc.Schemas.Add(Nothing, xsdFilePath)
    Dim errorBuilder As New XmlValidationErrorBuilder()
    doc.Validate(New ValidationEventHandler(AddressOf errorBuilder.ValidationEventHandler))
    Dim errorsText As List(Of String) = errorBuilder.GetErrors()
End Sub
End Class

Public Class XmlValidationErrorBuilder
Private _errors As New List(Of ValidationEventArgs)()

Public Sub ValidationEventHandler(ByVal sender As Object, ByVal args As ValidationEventArgs)
    If args.Severity = XmlSeverityType.Error Then
        _errors.Add(args)
    End If
End Sub

Public Function GetErrors() As List(Of String)
    If _errors.Count <> 0 Then
        Dim ErrorList As New List(Of String)

        For i As Integer = 0 To _errors.Count - 1
            Dim Message As String = _errors(i).Message
            Dim LineNumber As String = _errors(i).Exception.LineNumber
            Dim LinePosition As String = _errors(i).Exception.LinePosition
            Dim combineString = Message & "|" & LineNumber & "|" & LinePosition
            ErrorList.Add(combineString)
        Next
        Return ErrorList
    Else
        Return Nothing
    End If
End Function

Any validation errors are stored in a List(Of ValidationEventArgs) and are later processed by the GetErrors function. My problem is that Exception.LineNumber and Exception.LinePosition always returns 0. How can I get the line number and line position of the error?