--- title: "Pattern redaction and highlighting with C# | Nutrient DCS" canonical_url: "https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/pattern-redaction-and-highlighting/" md_url: "https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/pattern-redaction-and-highlighting.md" last_updated: "2026-05-23T00:08:18.015Z" description: "Implement pattern redaction and highlighting in documents using C# and Nutrient Document Converter Services. Secure sensitive information with regex patterns." --- # Pattern redaction and highlighting with C# This guide demonstrates how to implement document security using pattern redaction and highlighting with Nutrient Document Converter Services (DCS). These complementary techniques help protect sensitive information while maintaining document usability. ## Understanding redaction vs highlighting **Pattern redaction** permanently removes sensitive content by replacing it with colored blocks. This approach is ideal for: - Protecting personal identifiable information (PII) in published documents - Compliance with data protection regulations (GDPR, HIPAA) - Creating sanitized versions for public distribution - Preventing unauthorized access to confidential data **Pattern highlighting** visually marks sensitive content without removing it. This approach is useful for: - Document review workflows where content needs verification - Training materials where sensitive data should be visible but marked - Audit processes requiring visibility of flagged information - Quality assurance checks before final redaction Both techniques use regular expressions to identify patterns such as social security numbers, credit card numbers, or custom sensitive data formats. ## Choosing the right approach **Use pattern redaction when**: - Documents will be shared externally or published - Regulatory compliance requires permanent data removal (GDPR "right to be forgotten") - Sensitive information must be completely inaccessible - Creating sanitized versions for public distribution **Use pattern highlighting when**: - Internal review processes require content verification - Audit trails need to show what was flagged before removal - Training or educational materials need visible sensitive data markers - Quality assurance workflows require human verification before final redaction **Common regex patterns** - Social Security Numbers: `\b\d{3}-\d{2}-\d{4}\b` - Credit Card Numbers: `\b\d{4}[\s-]?\d{4}[\s-]?\d{4}[\s-]?\d{4}\b` - Email Addresses: `\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b` - Phone Numbers: `\b\d{3}[-.]?\d{3}[-.]?\d{4}\b` ## Prerequisites Before implementing pattern redaction and highlighting, ensure you have: - Nutrient Document Converter Services installed and running -.NET Framework or.NET Core development environment - Sample PDF documents for testing security operations - Implemented `OpenService` and `CloseService` methods from the [`DocumentConverterServiceClient`](https://www.nutrient.io/guides/document-converter/document-converter-services/knowledge-base/open-and-close-documentconverterserviceclient/) sample code - Basic understanding of regular expressions for pattern matching - Appropriate file system permissions for reading input files and writing output For initial DCS setup, refer to the [Document Converter Services installation](https://www.nutrient.io/guides/document-converter/document-converter-services.md) guide. ## Pattern redaction and highlighting with the API The following table outlines the properties used in pattern redaction and highlighting operations: | Property | Description | | --------------- | ------------------------------------------------------------------------------------------------------ | | `Debug` | Debug mode gives additional logging information. | | `Pattern` | Regular expression pattern for the text to be redacted/highlighted. | | `CaseSensitive` | The regular expression is case sensitive. | | `Red` | Red component of the highlight/redaction color. Range 0–255. | | `Green` | Green component of the highlight/redaction color. Range 0–255. | | `Blue` | Blue component of the highlight/redaction color. Range 0–255. | | `Alpha` | Alpha value, only used in the pattern highlighting operation. Range 0–255, fixed at 255 for redaction. | ## Example The following example demonstrates how to perform pattern redaction using the API: ```csharp /// /// Perform pattern redaction on the supplied file, writing the result into the target folder. /// /// URL endpoint for the PDF Converter service. /// Source filename. /// Target folder to receive the output file. static void PatternRedaction(string ServiceURL, string sourceFileName, string targetFolder) { DocumentConverterServiceClient client = null; try { // Create minimum `OpenOptions` object. OpenOptions openOptions = new OpenOptions(); openOptions.OriginalFileName = Path.GetFileName(sourceFileName); // Create minimum `PatternRedactionSettings`. PatternRedactionSettings patternRedactionSettings = new PatternRedactionSettings(); // Set what needs to be redacted. patternRedactionSettings.Red = 0; patternRedactionSettings.Green = 0; patternRedactionSettings.Blue = 255; patternRedactionSettings.Pattern = "\"374245455400126\""; // Create target folder if required. if (!Directory.Exists(targetFolder)) { Directory.CreateDirectory(targetFolder); } // ** Read the source file into a byte array. byte[] sourceFile = File.ReadAllBytes(sourceFileName); // ** Open the service and configure the bindings. client = OpenService(ServiceURL); // ** Carry out the conversion. byte[] result = client.PatternRedaction(sourceFile, openOptions, patternRedactionSettings); // ** Save the results. if (result!= null) { if (!Directory.Exists(targetFolder)) { Directory.CreateDirectory(targetFolder); } string filename = Path.GetFileNameWithoutExtension(sourceFileName); string destinationFileName = Path.GetFullPath(Path.Combine(targetFolder, filename + "-redacted.pdf")); using (FileStream fs = File.Create(destinationFileName)) { fs.Write(result, 0, result.Length); fs.Close(); } Console.WriteLine("File converted to " + destinationFileName); // Open the destination file. ProcessStartInfo psi = new ProcessStartInfo(); psi.FileName = destinationFileName; psi.UseShellExecute = true; Process.Start(psi); } else { Console.WriteLine("Nothing returned"); } } catch (FaultException ex) { Console.WriteLine($"FaultException occurred: ExceptionType: {ex.Detail.ExceptionType.ToString()}"); Console.WriteLine(); Console.WriteLine($"Error Detail: {string.Join(Environment.NewLine, ex.Detail.ExceptionDetails)}"); Console.WriteLine($"Error message: {ex.Message}"); Console.WriteLine(); Console.WriteLine($"Error reason: {ex.Reason}"); } catch (Exception ex) { Console.WriteLine(ex.Message); Console.WriteLine(ex.StackTrace); Console.WriteLine(ex.Data.ToString()); } finally { if (client!= null) { CloseService(client); } } } ``` For a practical demonstration, refer to the sample codes for [pattern redaction](https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/code-samples.md#pattern-redaction-sample-code) and [highlighting](https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/code-samples.md#pattern-highlighting-sample-code). ## Troubleshooting **Pattern matching error: Pattern not found** - Verify that the pattern exists in the document content - Check pattern syntax and escape special characters - Ensure the pattern format matches the document content structure - Test your regex pattern with online regex validators **Security operation error: Permission denied** - Verify that the application has read access to source documents - Check that the output directory has write permissions - Ensure documents aren’t password-protected or locked by other applications **Service connection error: Cannot connect to DCS** - Ensure Nutrient Document Converter Services is running and accessible - Verify the service URL in your code matches your DCS installation - Check that no firewall is blocking the connection **Color configuration issues: Redaction/highlighting not visible** - For redaction — Verify RGB values create visible blocks (avoid transparent colors) - For highlighting — Ensure Alpha value is appropriate (128 recommended for semi-transparency) - Check that color values are distinct from document background - Test with high-contrast colors first (for example, red for redaction, yellow for highlighting) **Performance issues: Slow processing** - Consider processing documents in batches for large volumes - Optimize pattern complexity to reduce processing time - Monitor memory usage for large documents - Use page ranges to limit processing scope when appropriate ## What’s next Now that you understand pattern redaction and highlighting concepts with C#, explore these related document security capabilities: - **Complete code examples** - Review comprehensive [sample code in C# for pattern redaction and highlighting](https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/code-samples.md) with detailed implementations - **Python implementation** - Compare approaches with [pattern highlighting using Python](https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/pattern-highlighting-using-python.md) for cross-language insights - **Smart redaction** - Discover automated sensitive data detection using [smart redaction](https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/smart-redaction.md) for advanced security workflows - **Document security overview** - Explore the complete [document security with C#](https://www.nutrient.io/guides/document-converter/document-converter-services/document-security/csharp.md) guide for more features --- ## Related pages - [Sample code in C# for pattern redaction and highlighting](/guides/document-converter/document-converter-services/document-security/code-samples.md) - [Secure PDF API](/guides/document-converter/document-converter-services/document-security.md) - [Secure and protect PDFs and Office documents in C#](/guides/document-converter/document-converter-services/document-security/csharp.md) - [Secure your PDFs and Office files easily with .NET](/guides/document-converter/document-converter-services/document-security/dotnet-core.md) - [Secure PDF and MS Office documents with Java](/guides/document-converter/document-converter-services/document-security/java.md) - [Secure PDF and Office documents with JavaScript](/guides/document-converter/document-converter-services/document-security/javascript.md) - [WSDL URL.](/guides/document-converter/document-converter-services/document-security/pattern-highlighting-using-python.md) - [WSDL URL.](/guides/document-converter/document-converter-services/document-security/pattern-redaction-using-python.md) - [Password protection for PDF documents in PHP](/guides/document-converter/document-converter-services/document-security/php.md) - [Smart document redaction with C#](/guides/document-converter/document-converter-services/document-security/smart-redaction.md)