Metadata Redaction

Metadata Redaction in C#

GroupDocs.Redaction(which is a part of Conholdate.Total for .NET) allows you to apply metadata redactions for documents of various formats like PDF, DOC, DOCX, PPT, PPTX, XLS, XLSX and others.

It provides a flexible API that enables you to replace or remove metadata using filters or search by regular expression.

Filter metadata

Base functionality for all redactions, derived from MetadataRedaction base class is metadata filtering and it is mandatory for metadata redactions. It uses flagged enumeration MetadataFilters, containing items for most frequent metadata entries. You can set the filter to All, or any combination of metadata. For instance, the example below sets filter to Author, Manager and NameOfApplication - for textual redaction or cleaning them out:

C#

// redaction derived from MetadataRedaction
redaction.Filter = MetadataFilters.Author | MetadataFilters.Manager | MetadataFilters.NameOfApplication;

Following is the table with full list of MetadataFilters items:

Clean metadata

Allows you to replace all or specific metadata in the document with empty (blank or minimal) values using EraseMetadataRedaction class. The example below blanks out all properties of the document:

C#

using (Redactor redactor = new Redactor(@"C:\sample.docx"))
{
   redactor.Apply(new EraseMetadataRedaction(MetadataFilters.All));

   redactor.Save();
}

You can specify MetadataFilter.All or use default constructor to blank out all metadata within given document, Custom - to clear all custom metadata entries.

Redact metadata

You can use MetadataSearchRedaction to remove sensitive data from document’s metadata using regular expressions. For instance, we can remove any mention of “Company Ltd.":

C#

using (Redactor redactor = new Redactor(@"C:\sample.docx"))
{
   redactor.Apply(new MetadataSearchRedaction("Company Ltd.", "--company--"));

   redactor.Save();
}

First argument is regular expression, second is a replacement string. You can also set scope for redaction by setting filter, e.g. to MetadataFilter.Company. - it will leave the regular expressions matches undone in all metadata items, except “Company” property:

C#

using (Redactor redactor = new Redactor(@"C:\sample.docx"))
{
   MetadataSearchRedaction redaction = new MetadataSearchRedaction("Company Ltd.", "--company--");
   redaction.Filter = MetadataFilters.Company;
   redactor.Apply(redaction);
   redactor.Save();
}

Metadata redaction status

All metadata redactions apply to each metadata item separately, and even if metadata item redaction fails, the rest of the metadata items will be updated. You can find a list of failed, skipped (rejected) metadata items and reasons for that in ErrorMessage property of RedactorLogEntry.Result.