How to open Word template, update some text, and save as .pdf in vb.net core

Question

I am working on a vb.net core console app that queries data from a database into a DataTable, opens a Word (.dot) template file, updates some text, and then saves as a .pdf without saving changes to the original template. Word is being very fussy. While debugging, if an exception is thrown, by the time I get to the catch block the Word.Application is gone, so I can't seem to exit gracefully, and apparently an instance is maintained in memory, as I have to reboot my machine to get the program to run again as Word won't start.

Is there a better way to interact with Word?

Here's my code:

Dim application As Word.Application = Nothing
Try
    application = New Word.Application With {.Visible = True}
    application.Documents.Open("C:\MattsFunctionReport.dot")
    Dim document = application.ActiveDocument
    
    'There are lots of these Items, just showing one as an example.                    
    If IsDBNull(row.Item("FunctionName"))
        document.Content.Find.Execute(FindText:="<<FunctionName>>", ReplaceWith:="", Replace:=WdReplace.wdReplaceAll)
    Else
        document.Content.Find.Execute(FindText:="<<FunctionName>>", ReplaceWith:=row.Item("FunctionName"), Replace:=WdReplace.wdReplaceAll)
    End If

    'save as PDF
    application.ActiveDocument.SaveAs2("C:\SampleOutput.pdf", WdSaveFormat.wdFormatPDF)

    'Close the document.
    application.Documents.Close(WdSaveOptions.wdDoNotSaveChanges)

    'Quit Word.Application
    application.Quit()
Catch ex As Exception
    'Close Word
    application.Documents.Close(WdSaveOptions.wdDoNotSaveChanges)
    application.Quit()
    'Show Exception
    ConsoleEx.WriteError(ex.Message)
    ConsoleEx.WriteLineInRed(ex.StackTrace)
    'Log Exception
    WriteLog(ex.ToString)
    Console.Writeline("Press any key to exit the program.")
    Console.ReadKey()
    End
End Try

This is the exception I get when I try to debug again without rebooting.

This is the exception when application.ActiveDocument.SaveAs("C:\SampleOutput.pdf", WdSaveFormat.wdFormatPDF)blows up..

Answer 1

The following shows how to open a .dot (or .dotx) Word template using Word interop in a .NET Console App, replace some text, and then export (ie: save) it as a PDF. For testing, I used .NET 6.

Try the following:

Add reference:

• Microsoft Word xx.x Object Library (ex: Microsoft Word 16.0 Object Library)

Add the following Imports statement:

• Imports Word = Microsoft.Office.Interop.Word

ModifyWordDoc:

Private Function ModifyWordDoc(filename As String, pdfFilename As String, Optional isVisible As Boolean = False) As String
    Dim wordApp As Word.Application = Nothing
    Dim document As Word.Document = Nothing

    Try
        'create new instance
        wordApp = New Word.Application() With {.Visible = isVisible}

        'create new document from template
        document = wordApp.Documents.Add(Template:=filename)

        'ToDo: add desired code

        document.Content.Find.Execute(FindText:="<<FunctionName>>", ReplaceWith:="TEST", Replace:=Word.WdReplace.wdReplaceAll)

        'export (ie: save) as PDF
        document.ExportAsFixedFormat(pdfFilename, Word.WdExportFormat.wdExportFormatPDF)

        Return "Successfully completed"
    Catch ex As Exception
        'ToDo: add desired code

        Debug.WriteLine($"Error (ModifyWordDoc) - {ex.Message}")
    Finally
        If document IsNot Nothing Then
            document.Close(Word.WdSaveOptions.wdDoNotSaveChanges)
        End If

        If wordApp IsNot Nothing Then
            wordApp.Quit()
        End If
    End Try

    Return "Unsuccessful"
End Function

Note: You may desire to return an Integer instead of a String.

Usage:

Sub Main(args As String())
    Dim filename As String = "C:\Temp\Test.dot"
    Dim pdfFilename As String = "C:\Temp\Test.pdf"
    Console.WriteLine($"Modifying Word document '{filename}'...")

    Dim result As String = ModifyWordDoc(filename, pdfFilename, True)
    Debug.WriteLine($"result: {result}")

    If result = "Successfully completed" Then
        Environment.Exit(0)
    Else
        Environment.Exit(-1)
    End If
End Sub

Resources:

• Microsoft.Office.Interop.Word Namespace
• Documents.Add(Object, Object, Object, Object) Method
• Document.ExportAsFixedFormat method
• WdExportFormat enumeration
• Printing pdf through automating word with VB net without showing dialog