ReplacingArgs.GroupIndex property

Identifies, by index, a captured group in the Match that is to be replaced with the Replacement string.

public int GroupIndex { get; set; }


GroupIndex has effect only when GroupName is null.

Default is zero.


Shows how to apply a different font to new content via FindReplaceOptions.

public void ConvertNumbersToHexadecimal()
    Document doc = new Document();
    DocumentBuilder builder = new DocumentBuilder(doc);

    builder.Font.Name = "Arial";
    builder.Writeln("Numbers that the find-and-replace operation will convert to hexadecimal and highlight:\n" +
                    "123, 456, 789 and 17379.");

    // We can use a "FindReplaceOptions" object to modify the find-and-replace process.
    FindReplaceOptions options = new FindReplaceOptions();

    // Set the "HighlightColor" property to a background color that we want to apply to the operation's resulting text.
    options.ApplyFont.HighlightColor = Color.LightGray;

    NumberHexer numberHexer = new NumberHexer();
    options.ReplacingCallback = numberHexer;

    int replacementCount = doc.Range.Replace(new Regex("[0-9]+"), "", options);


    Assert.AreEqual(4, replacementCount);
    Assert.AreEqual("Numbers that the find-and-replace operation will convert to hexadecimal and highlight:\r" +
                    "0x7B, 0x1C8, 0x315 and 0x43E3.", doc.GetText().Trim());
    Assert.AreEqual(4, doc.GetChildNodes(NodeType.Run, true).OfType<Run>()
            .Count(r => r.Font.HighlightColor.ToArgb() == Color.LightGray.ToArgb()));

/// <summary>
/// Replaces numeric find-and-replacement matches with their hexadecimal equivalents.
/// Maintains a log of every replacement.
/// </summary>
private class NumberHexer : IReplacingCallback
    public ReplaceAction Replacing(ReplacingArgs args)

        int number = Convert.ToInt32(args.Match.Value);

        args.Replacement = $"0x{number:X}";

        mLog.AppendLine($"Match #{mCurrentReplacementNumber}");
        mLog.AppendLine($"\tOriginal value:\t{args.Match.Value}");
        mLog.AppendLine($"\tOffset in parent {args.MatchNode.NodeType} node:\t{args.MatchOffset}");

            ? $"\tGroup index:\t{args.GroupIndex}"
            : $"\tGroup name:\t{args.GroupName}");

        return ReplaceAction.Replace;

    public string GetLog()
        return mLog.ToString();

    private int mCurrentReplacementNumber;
    private readonly StringBuilder mLog = new StringBuilder();

See Also