DocumentFormatInstance .cs

// For complete examples and data files, please go to https://github.com/groupdocs-redaction/GroupDocs.Redaction-for-.NET
public class PlainTextDocument : DocumentFormatInstance, ITextualFormatInstance
{
    private RedactorSettings Settings { get; set; }
    private List<string> FileContent { get; set; }

    public PlainTextDocument()
    {
        FileContent = new List<string>();
    }

    public override void Initialize(DocumentFormatConfiguration config, RedactorSettings settings)
    {
        Settings = settings;
    }

    public override void Load(System.IO.Stream input)
    {
        FileContent.Clear();
        using (var reader = new StreamReader(input))
        {
            string line = string.Empty;
            do
            {
                line = reader.ReadLine();
                if (!string.IsNullOrEmpty(line))
                {
                    FileContent.Add(line);
                }
            }
            while (!string.IsNullOrEmpty(line));
            reader.Close();
        }
    }

	public override void Save(System.IO.Stream output)
    {
        using (var writer = new StreamWriter(output)) 
        {
            foreach (var line in FileContent)
            {
                writer.WriteLine(line);
            }
            writer.Close();
        }
    }

    public RedactionResult ReplaceText(Regex regex, Redactions.ReplacementOptions options)
    {
        try
        {
            if (options.ActionType != Redactions.ReplacementType.ReplaceString)
            {
                return new RedactionResult.Failed("This format allows only ReplaceString redactions!");
            }
            for (int i = 0; i < FileContent.Count; i++)
            {
                FileContent[i] = regex.Replace(FileContent[i], options.Replacement);
            }
            return RedactionResult.Successful();
        }
        catch (Exception ex)
        {
            return RedactionResult.Failed(ex.ToString());
        }
    }
}