Question

Using C#, is there a good way to find and replace a text string in a docx file without having word installed on that machine?

Answer 1

Yes, using Open XML. Here’s an article which addresses your specific question: Creating a Simple Search and Replace Utility for Word 2007 Open XML Format Documents

To work with this file format, one option is to use the Open XML
Format Application Programming Interface (API) in the
DocumentFormat.OpenXml.Packaging namespace. The classes, methods, and
properties in this namespace are located in the
DocumentFormat.OpenXml.dll file. You can install this DLL file by
installing the Open XML Format SDK version 1.0. The members in this
namespace allow you to easily work with the package contents for Excel
2007 workbooks, PowerPoint 2007 presentations, and Word 2007
documents.

…

Private Sub Search_Replace(ByVal file As String)
Dim wdDoc As WordprocessingDocument = WordprocessingDocument.Open(file, True)

' Manage namespaces to perform Xml XPath queries.
Dim nt As NameTable = New NameTable
Dim nsManager As XmlNamespaceManager = New XmlNamespaceManager(nt)
nsManager.AddNamespace("w", wordmlNamespace)

' Get the document part from the package.
Dim xdoc As XmlDocument = New XmlDocument(nt)
' Load the XML in the part into an XmlDocument instance.
xdoc.Load(wdDoc.MainDocumentPart.GetStream)

' Get the text nodes in the document.
Dim nodes As XmlNodeList = Nothing
nodes = xdoc.SelectNodes("//w:t", nsManager)
Dim node As XmlNode
Dim nodeText As String = ""

' Make the swap.
Dim oldText As String = txtOldText.Text
Dim newText As String = txtNewText.Text
For Each node In nodes
   nodeText = node.FirstChild.InnerText
   If (InStr(nodeText, oldText) > 0) Then
      nodeText = nodeText.Replace(oldText, newText)
      ' Increment the occurrences counter.
      numChanged += 1
   End If
Next

' Write the changes back to the document.
xdoc.Save(wdDoc.MainDocumentPart.GetStream(FileMode.Create))

' Display the number of change occurrences.
txtNumChanged.Text = numChanged
End Sub