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Find Text in Word DOCX Document using regex & Replace it with Hyperlink using C# .NET | Find Replace Direction Backward

I am trying to find text in docx file that match a regex(any combination of strings and numbers with “/” such as Link/Link/1/1 ) and replace all matches with a hyperlink, I am using the following code but always getting error with the split run function

Error: startIndex cannot be larger than length of string.
Parameter name: startIndex

public void addhyperlinks(string source)
Document doc = new Document(source);
FindReplaceOptions options = new FindReplaceOptions();
options.ReplacingCallback = new ReplaceWithHyperlinkEvaluator();
doc.Range.Replace(new Regex(@"[A-Za-z]+/[/A-Za-z0-9]+"),string.Empty, options);

internal class ReplaceWithHyperlinkEvaluator : IReplacingCallback
    string link="www.google.com/";
    //public FindAndInsertHyperlink(string text, string link)
    ReplaceAction IReplacingCallback.Replacing(ReplacingArgs args)


        // This is a Run node that contains either the beginning or the complete match.

        Node currentNode = args.MatchNode;

        // The first (and may be the only) run can contain text before the match,

        // in this case it is necessary to split the run.

        if (args.MatchOffset > 0)
        { currentNode = SplitRun((Run)currentNode, args.MatchOffset); }
        // This array is used to store all nodes of the match for further removing.
        ArrayList runs = new ArrayList();
        // Find all runs that contain parts of the match string.
        int remainingLength = args.Match.Value.Length;
        while (

        (remainingLength > 0) &&

        (currentNode != null) &&

        (currentNode.GetText().Length <= remainingLength))



            remainingLength = remainingLength - currentNode.GetText().Length;

            // Select the next Run node.

            // Have to loop because there could be other nodes such as BookmarkStart etc.



                currentNode = currentNode.NextSibling;


            while ((currentNode != null) && (currentNode.NodeType != NodeType.Run));


        // Split the last run that contains the match if there is any text left.

        if ((currentNode != null) && (remainingLength > 0))


            SplitRun((Run)currentNode, remainingLength);



        // Create DocumentBuilder and move its cursor to the match node.

        DocumentBuilder builder = new DocumentBuilder((Document)args.MatchNode.Document);


        // Insert Hyperlink

        builder.Font.StyleIdentifier = StyleIdentifier.Hyperlink;

        builder.InsertHyperlink(args.Match.Value, link + args.Match.Value, false);

        // Now remove all runs in the sequence.

        foreach (Run run in runs)

        // Signal to the replace engine to do nothing because we have already done all what we wanted.
        return ReplaceAction.Skip;


    /// Splits text of the specified run into two runs.

    /// Inserts the new run just after the specified run.


    private static Run SplitRun(Run run, int position)


        Run afterRun = (Run)run.Clone(true);

        afterRun.Text = run.Text.Substring(position);

        run.Text = run.Text.Substring(0, position);

        run.ParentNode.InsertAfter(afterRun, run);

        return afterRun;



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  • Your simplified input Word document
  • Aspose.Words 20.5 generated output DOCX file showing the undesired behavior
  • Your expected DOCX file showing the desired output. You can create this document by using MS Word.

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Thanks for your response
Please find attached the input file you requested HyperlinkError.docx and the expected result HyperlinkError - Result.docx
When trying to find all text that matches my regex in HyperlinkError.docx I am getting an error
Error: startIndex cannot be larger than length of string.
Parameter name: startIndex

Demo.zip (35.7 KB)


Please either use the FindReplaceOptions options = new FindReplaceOptions(FindReplaceDirection.Backward); constructor overload or try specifying the direction using the following C# code:

Document doc = new Document("E:\\Temp\\Demo\\HyperlinkError.docx");
FindReplaceOptions options = new FindReplaceOptions();
options.Direction = FindReplaceDirection.Backward;
options.ReplacingCallback = new ReplaceWithHyperlinkEvaluator();
doc.Range.Replace(new Regex(@"[A-Za-z]+/[/A-Za-z0-9]+"), "", options);

Hope, this helps.

1 Like

Great I tested fast it works great I will do more tests and will come back to you in case

Thanks again


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