InfoPath Dev

It has been a long day and this code is giving me this error.

System.NullReferenceException
Object reference not set to an instance of an object.
   at DPR_Library_5.FormCode.CTRL177_5_Clicked(Object sender, ClickedEventArgs e) in \\srv-na01\user\rep\InfoPath Projects\DPR_Library_Final_1_GetFile\FormCode.vb:line 76
   at Microsoft.Office.InfoPath.Internal.ButtonEventHost.OnButtonClick(DocActionEvent pEvent)
   at Microsoft.Office.Interop.InfoPath.SemiTrust._ButtonEventSink_SinkHelper.OnClick(DocActionEvent pEvent)

 Public Sub CTRL177_5_Clicked(ByVal sender As Object, ByVal e As ClickedEventArgs)       

            Dim openFileDialog1 As New OpenFileDialog()

            openFileDialog1.InitialDirectory = "G:\"

            openFileDialog1.Filter = "All files (*.*)|*.*"

            openFileDialog1.FilterIndex = 2

            openFileDialog1.RestoreDirectory = True

            If openFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then

                Dim uri As New Uri(openFileDialog1.FileName)

                Dim first As XPathNavigator = MainDataSource.CreateNavigator(). _

                SelectSingleNode("/my:myFields/my:DPR_Library_5/my:group4/my:artworkLocation", NamespaceManager)

                If first.Value Is "" Then

                    MainDataSource.CreateNavigator(). _

                    SelectSingleNode("/my:myFields/my:DPR_Library_5/my:group4/my:artworkLocation", NamespaceManager). _

                    SetValue(uri.OriginalString)

                Else

                    Dim myNamespace As String = NamespaceManager.LookupNamespace("my")

                    Using writer As XmlWriter = MainDataSource.CreateNavigator().SelectSingleNode( _

                   "/my:myFields/my:DPR_Library_5", NamespaceManager).AppendChild()

                        writer.WriteStartElement("group4", myNamespace)

                        writer.WriteElementString("artworkLocation", myNamespace, uri.OriginalString)

                        writer.WriteEndElement()

                        writer.Close()

                    End Using

                End If

            End If

        End Sub

Which line is line 76?

My suspect would be this line:

 If first.Value Is "" Then

Because if the variable "first" is NULL, it would throw this error when you tried to get it's value.

Do you know how to run your code in debug? (I don't mean that question to be patronizing, just sometimes we see that - here's a blog post to help if you don't know how.) That can help you track down the error.

I know how to run it in in debug I had been up for 15 hours and exhausted, I did not see the line 76 on my screen as I was remotely connected until I posted.

I changed my code and fixed the error.

Thanks for the reply.