GroupDocs Signature NET Tutorial - Complete Event Handling Guide
Introduction
Struggling with document signature management in your .NET applications? You’re not alone. Many developers find themselves overwhelmed when trying to implement robust digital signature solutions that actually work in production environments.
Here’s the good news: GroupDocs.Signature for .NET makes this whole process much more manageable than you might think. This comprehensive tutorial will walk you through everything you need to know about subscribing to search events and configuring barcode signature searches - the kind of stuff that actually matters when you’re building real applications.
By the time you finish reading this guide, you’ll be able to:
- Set up event handling that gives you real-time insights into document processing
- Configure barcode search parameters that find exactly what you’re looking for
- Troubleshoot common issues before they become production headaches
- Implement these features in ways that make sense for your specific use case
Whether you’re building a document management system, compliance tool, or just need to add signature verification to an existing app, this tutorial has got you covered.
Why Event Handling Matters in Document Processing
Before we dive into the code, let’s talk about why you’d want to handle events in the first place. When you’re processing documents (especially large ones or batches), you need visibility into what’s happening. Are things progressing? Did something go wrong? How long is this going to take?
Without proper event handling, your users are stuck staring at a loading spinner with no idea if your application is working or crashed. That’s not a great experience, and it makes debugging a nightmare when things do go wrong.
The event system in GroupDocs.Signature gives you hooks into the entire search process, so you can:
- Show progress bars that actually mean something
- Log detailed information for troubleshooting
- Cancel long-running operations if needed
- Trigger other actions based on what’s found (or not found)
Setting Up GroupDocs.Signature for .NET
First things first - let’s get the library installed. If you’ve done this before, feel free to skip ahead, but I’ll cover the basics for anyone who’s new to this.
Installation Options
You’ve got several ways to add GroupDocs.Signature to your project:
.NET CLI (my personal favorite for new projects):
dotnet add package GroupDocs.Signature
Package Manager Console (if you’re working in Visual Studio):
Install-Package GroupDocs.Signature
NuGet Package Manager UI: Just search for “GroupDocs.Signature” and hit install.
Licensing Considerations
Here’s something important that a lot of tutorials skip: licensing. GroupDocs.Signature isn’t free, but they make it easy to get started:
- Free Trial: Perfect for evaluation and learning (which is what we’re doing here)
- Temporary License: Good for extended testing periods
- Full License: Required for production use
You can grab a temporary license from their website if you need more time than the trial provides.
Basic Setup
Once you’ve got the package installed, here’s the basic pattern you’ll use throughout this tutorial:
using System;
using GroupDocs.Signature;
string filePath = @"YOUR_DOCUMENT_DIRECTORY/"; // Replace with your actual document path
using (Signature signature = new Signature(filePath))
{
// All your signature operations go here
}
The using statement is important here - it ensures that resources are properly cleaned up when you’re done, which is crucial for performance in production applications.
Subscribing to Document Search Events
Now let’s get into the meat of this tutorial. Event subscription in GroupDocs.Signature follows the standard .NET event pattern, so if you’ve worked with events before, this will feel familiar.
Understanding the Available Events
GroupDocs.Signature provides three main events during the search process:
- SearchStarted: Fires when the search begins (great for showing “Processing…” messages)
- SearchProgress: Fires periodically during processing (perfect for progress bars)
- SearchCompleted: Fires when everything’s done (ideal for cleanup and final reporting)
Setting Up Event Handlers
Here’s how you create handlers for each event. I like to keep these as private static methods, but you can organize them however makes sense for your application:
private static void OnSearchStarted(Signature sender, ProcessStartEventArgs args)
{
Console.WriteLine($"Search started. Processing {args.TotalSignatures} signatures...");
// This is where you'd update your UI, start a progress bar, etc.
}
private static void OnSearchProgress(Signature sender, ProcessProgressEventArgs args)
{
Console.WriteLine($"Progress: {args.ProcessedSignatures}/{args.TotalSignatures} " +
$"({args.Progress}%) - Time elapsed: {args.Ticks}ms");
// Update progress bars, check for cancellation requests, etc.
}
private static void OnSearchCompleted(Signature sender, ProcessCompleteEventArgs args)
{
Console.WriteLine($"Search completed! Found {args.ProcessedSignatures} signatures " +
$"in {args.Ticks}ms");
// Clean up, show results, trigger next actions, etc.
}
Wiring Up the Events
Here’s how you connect these handlers to the actual signature object:
string filePath = @"YOUR_DOCUMENT_DIRECTORY/sample.pdf";
using (Signature signature = new Signature(filePath))
{
// Subscribe to events
signature.SearchStarted += OnSearchStarted;
signature.SearchProgress += OnSearchProgress;
signature.SearchCompleted += OnSearchCompleted;
// Now when you perform searches, these events will fire
// (We'll cover the actual search operations next)
}
Real-World Event Handling Tips
In production applications, you’ll want to do more than just write to the console. Here are some practical patterns I’ve found useful:
Progress Tracking: Use a Progress<T> object to report progress back to the UI thread:
private static void OnSearchProgress(Signature sender, ProcessProgressEventArgs args)
{
// Assuming you have a Progress<int> passed in somehow
progressReporter?.Report(args.Progress);
}
Logging: Integrate with your logging framework (Serilog, NLog, etc.):
private static void OnSearchStarted(Signature sender, ProcessStartEventArgs args)
{
logger.LogInformation("Document search started for {TotalSignatures} signatures",
args.TotalSignatures);
}
Error Handling: While these events don’t directly handle errors, you can use them to detect when things might be going wrong (like if progress stops updating).
Configuring Barcode Search Options
Now that we’ve got event handling sorted out, let’s dive into the actual search configuration. This is where you tell GroupDocs.Signature exactly what you’re looking for and where to look for it.
Understanding BarcodeSearchOptions
The BarcodeSearchOptions class gives you fine-grained control over your search. Here are the key properties you’ll work with:
- AllPages: Whether to search every page (can be slow for large documents)
- PageNumber: Start searching from a specific page
- PagesSetup: More complex page selection (odd pages, even pages, ranges, etc.)
- MatchType: How to match the barcode text
- Text: What text pattern to look for
Basic Search Configuration
Here’s a straightforward example that searches the first page for a specific barcode:
string filePath = @"YOUR_DOCUMENT_DIRECTORY/document_with_barcodes.pdf";
using (Signature signature = new Signature(filePath))
{
// Set up your event handlers first
signature.SearchStarted += OnSearchStarted;
signature.SearchProgress += OnSearchProgress;
signature.SearchCompleted += OnSearchCompleted;
// Configure search options
BarcodeSearchOptions options = new BarcodeSearchOptions()
{
AllPages = false, // Don't search every page
PageNumber = 1, // Start from page 1
MatchType = TextMatchType.Contains, // Look for text that contains our pattern
Text = "12345" // The barcode text we're searching for
};
// Execute the search
List<BarcodeSignature> signatures = signature.Search<BarcodeSignature>(options);
Console.WriteLine($"Found {signatures.Count} barcode signatures");
}
Advanced Page Selection
Sometimes you need more control over which pages to search. The PagesSetup property lets you get really specific:
BarcodeSearchOptions options = new BarcodeSearchOptions()
{
AllPages = false,
PagesSetup = new PagesSetup()
{
FirstPage = true, // Include the first page
LastPage = true, // Include the last page
OddPages = false, // Skip odd pages
EvenPages = false // Skip even pages
},
MatchType = TextMatchType.Exact,
Text = "SIGNATURE_123"
};
This configuration would search only the first and last pages for an exact match of “SIGNATURE_123”.
Text Matching Strategies
The MatchType property is crucial for finding what you’re looking for. Here are your options:
- Exact: The barcode text must match exactly
- StartsWith: The barcode text must start with your pattern
- EndsWith: The barcode text must end with your pattern
- Contains: The barcode text must contain your pattern somewhere
Choose based on what you know about your barcodes. If you’re dealing with standardized formats, Exact is usually best. If you’re looking for barcodes that might have prefixes or suffixes, Contains gives you more flexibility.
Performance Considerations
Here’s something important that doesn’t get talked about enough: barcode searching can be resource-intensive, especially on large documents. Here are some tips to keep things running smoothly:
Limit Your Search Scope: Don’t use AllPages = true unless you really need to. If you know your barcodes are typically on the first or last page, specify that.
Use Specific Text Patterns: The more specific your search text, the faster the search will be.
Consider Timeouts: For very large documents, you might want to implement timeout logic to prevent searches from running indefinitely.
Common Issues and How to Solve Them
Let’s talk about the problems you’re likely to run into and how to fix them. I’ve seen these issues come up repeatedly, so addressing them upfront will save you time.
Issue 1: Events Not Firing
Symptom: Your event handlers are set up correctly, but they never get called.
Cause: Usually this happens when you subscribe to events after performing the search, or when there’s an exception that prevents the search from starting.
Solution: Always subscribe to events before calling any search methods, and wrap your search calls in try-catch blocks:
using (Signature signature = new Signature(filePath))
{
// Subscribe FIRST
signature.SearchStarted += OnSearchStarted;
signature.SearchProgress += OnSearchProgress;
signature.SearchCompleted += OnSearchCompleted;
try
{
// Then search
var results = signature.Search<BarcodeSignature>(options);
}
catch (Exception ex)
{
Console.WriteLine($"Search failed: {ex.Message}");
}
}
Issue 2: Poor Search Performance
Symptom: Searches take a really long time, especially on larger documents.
Cause: Usually you’re searching too broadly (all pages) or your text matching is too generic.
Solution: Be more specific with your search parameters:
// Instead of this (slow):
BarcodeSearchOptions slowOptions = new BarcodeSearchOptions()
{
AllPages = true,
MatchType = TextMatchType.Contains,
Text = "1" // Too generic!
};
// Do this (fast):
BarcodeSearchOptions fastOptions = new BarcodeSearchOptions()
{
AllPages = false,
PageNumber = 1, // Or specific pages where you expect barcodes
MatchType = TextMatchType.StartsWith,
Text = "INVOICE_" // More specific pattern
};
Issue 3: No Results When You Expect Them
Symptom: Your search completes successfully but finds zero results, even though you know there are barcodes in the document.
Cause: This usually happens because of mismatched text patterns or searching the wrong pages.
Solution: Start with a broader search and narrow it down:
// First, try a very broad search to see what's there
BarcodeSearchOptions broadSearch = new BarcodeSearchOptions()
{
AllPages = true,
MatchType = TextMatchType.Contains,
Text = "" // Empty string matches everything
};
var allResults = signature.Search<BarcodeSignature>(broadSearch);
foreach (var result in allResults)
{
Console.WriteLine($"Found barcode: '{result.Text}' on page {result.PageNumber}");
}
This will show you exactly what barcodes exist and what their text looks like, so you can adjust your search parameters accordingly.
Issue 4: Memory Issues with Large Documents
Symptom: Your application runs out of memory or becomes very slow when processing large documents.
Cause: Not properly disposing of resources, or trying to process too much at once.
Solution: Always use using statements and consider processing documents in smaller chunks:
// Good - properly disposed
using (Signature signature = new Signature(filePath))
{
// Process here
}
// For very large documents, consider searching specific page ranges
for (int page = 1; page <= totalPages; page += 10) // Process 10 pages at a time
{
using (Signature signature = new Signature(filePath))
{
BarcodeSearchOptions options = new BarcodeSearchOptions()
{
PageNumber = page,
// Set up page range for next 10 pages
};
var results = signature.Search<BarcodeSignature>(options);
// Process results immediately, don't accumulate them all
}
}
Real-World Implementation Examples
Let’s look at some practical scenarios where you’d use these features in actual applications.
Scenario 1: Invoice Processing System
Imagine you’re building a system that processes invoices automatically. Each invoice has a barcode with the invoice number, and you need to extract that information.
public async Task<string> ExtractInvoiceNumber(string invoicePath)
{
using (Signature signature = new Signature(invoicePath))
{
signature.SearchProgress += (sender, args) => {
// Update progress bar for user feedback
Console.WriteLine($"Processing invoice: {args.Progress}%");
};
BarcodeSearchOptions options = new BarcodeSearchOptions()
{
AllPages = false,
PageNumber = 1, // Invoice numbers are typically on the first page
MatchType = TextMatchType.StartsWith,
Text = "INV-" // All invoice numbers start with "INV-"
};
var results = signature.Search<BarcodeSignature>(options);
if (results.Any())
{
return results.First().Text; // Return the first matching invoice number
}
throw new InvalidOperationException("No invoice number found in document");
}
}
Scenario 2: Document Verification Service
Here’s how you might build a service that verifies the authenticity of documents by checking for specific security barcodes:
public class DocumentVerificationService
{
private readonly ILogger<DocumentVerificationService> _logger;
public DocumentVerificationService(ILogger<DocumentVerificationService> logger)
{
_logger = logger;
}
public async Task<bool> VerifyDocumentAuthenticity(string documentPath, string expectedSecurityCode)
{
try
{
using (Signature signature = new Signature(documentPath))
{
signature.SearchStarted += (sender, args) => {
_logger.LogInformation("Starting verification of {DocumentPath}", documentPath);
};
signature.SearchCompleted += (sender, args) => {
_logger.LogInformation("Verification completed in {ElapsedMs}ms", args.Ticks);
};
BarcodeSearchOptions options = new BarcodeSearchOptions()
{
AllPages = true, // Security codes could be anywhere
MatchType = TextMatchType.Exact,
Text = expectedSecurityCode
};
var results = signature.Search<BarcodeSignature>(options);
return results.Any();
}
}
catch (Exception ex)
{
_logger.LogError(ex, "Error verifying document {DocumentPath}", documentPath);
return false;
}
}
}
Scenario 3: Batch Document Processing
For processing multiple documents, you’d want robust error handling and progress reporting:
public async Task<List<ProcessingResult>> ProcessDocumentBatch(List<string> documentPaths)
{
var results = new List<ProcessingResult>();
int completed = 0;
foreach (string path in documentPaths)
{
try
{
using (Signature signature = new Signature(path))
{
signature.SearchProgress += (sender, args) => {
// Report overall batch progress
double overallProgress = (completed / (double)documentPaths.Count) * 100;
Console.WriteLine($"Batch progress: {overallProgress:F1}% (Document {completed + 1}/{documentPaths.Count})");
};
var searchResults = signature.Search<BarcodeSignature>(new BarcodeSearchOptions()
{
AllPages = true,
MatchType = TextMatchType.Contains,
Text = "" // Find all barcodes
});
results.Add(new ProcessingResult
{
DocumentPath = path,
Success = true,
BarcodesFound = searchResults.Count
});
}
}
catch (Exception ex)
{
results.Add(new ProcessingResult
{
DocumentPath = path,
Success = false,
Error = ex.Message
});
}
finally
{
completed++;
}
}
return results;
}
public class ProcessingResult
{
public string DocumentPath { get; set; }
public bool Success { get; set; }
public int BarcodesFound { get; set; }
public string Error { get; set; }
}
Performance Optimization Tips
When you’re working with GroupDocs.Signature in production, performance matters. Here are some strategies I’ve learned from experience:
1. Optimize Search Parameters
The more specific you can be about what you’re looking for and where, the faster your searches will be:
// Slow - searches everywhere for anything
BarcodeSearchOptions slowOptions = new BarcodeSearchOptions()
{
AllPages = true,
MatchType = TextMatchType.Contains,
Text = ""
};
// Fast - searches specific location for specific pattern
BarcodeSearchOptions fastOptions = new BarcodeSearchOptions()
{
AllPages = false,
PageNumber = 1,
MatchType = TextMatchType.StartsWith,
Text = "KNOWN_PREFIX"
};
2. Use Appropriate Disposal Patterns
Always use using statements or properly dispose of Signature objects:
// Good
using (var signature = new Signature(filePath))
{
// Work with signature
}
// Also good
var signature = new Signature(filePath);
try
{
// Work with signature
}
finally
{
signature.Dispose();
}
3. Consider Async Patterns
While GroupDocs.Signature doesn’t provide async methods directly, you can wrap the operations to avoid blocking the UI thread:
public async Task<List<BarcodeSignature>> SearchBarcodesAsync(string filePath, BarcodeSearchOptions options)
{
return await Task.Run(() =>
{
using (var signature = new Signature(filePath))
{
return signature.Search<BarcodeSignature>(options);
}
});
}
4. Cache Results When Appropriate
If you’re searching the same documents repeatedly, consider caching the results:
private static readonly Dictionary<string, List<BarcodeSignature>> _searchCache =
new Dictionary<string, List<BarcodeSignature>>();
public List<BarcodeSignature> SearchWithCaching(string filePath, BarcodeSearchOptions options)
{
string cacheKey = $"{filePath}:{options.GetHashCode()}";
if (_searchCache.ContainsKey(cacheKey))
{
return _searchCache[cacheKey];
}
using (var signature = new Signature(filePath))
{
var results = signature.Search<BarcodeSignature>(options);
_searchCache[cacheKey] = results;
return results;
}
}
Integration Best Practices
Here are some patterns I’ve found work well when integrating GroupDocs.Signature into larger applications:
1. Dependency Injection
If you’re using dependency injection, create a service wrapper:
public interface IDocumentSignatureService
{
Task<List<BarcodeSignature>> SearchBarcodesAsync(string filePath, BarcodeSearchOptions options);
event EventHandler<ProgressEventArgs> ProgressReported;
}
public class DocumentSignatureService : IDocumentSignatureService
{
public event EventHandler<ProgressEventArgs> ProgressReported;
public async Task<List<BarcodeSignature>> SearchBarcodesAsync(string filePath, BarcodeSearchOptions options)
{
return await Task.Run(() =>
{
using (var signature = new Signature(filePath))
{
signature.SearchProgress += (sender, args) =>
{
ProgressReported?.Invoke(this, new ProgressEventArgs(args.Progress));
};
return signature.Search<BarcodeSignature>(options);
}
});
}
}
2. Configuration Management
Store common search configurations in your app settings:
{
"DocumentProcessing": {
"DefaultSearchOptions": {
"AllPages": false,
"StartPage": 1,
"MatchType": "StartsWith",
"CommonPrefixes": ["INV-", "DOC-", "REF-"]
}
}
}
3. Error Handling Strategy
Develop a consistent error handling approach:
public class DocumentProcessingException : Exception
{
public string DocumentPath { get; }
public DocumentProcessingException(string documentPath, string message, Exception innerException)
: base(message, innerException)
{
DocumentPath = documentPath;
}
}
public List<BarcodeSignature> SearchBarcodes(string filePath, BarcodeSearchOptions options)
{
try
{
using (var signature = new Signature(filePath))
{
return signature.Search<BarcodeSignature>(options);
}
}
catch (Exception ex)
{
throw new DocumentProcessingException(filePath,
$"Failed to search barcodes in document: {ex.Message}", ex);
}
}
Conclusion
You’ve now learned how to effectively use GroupDocs.Signature for .NET to handle document search events and configure barcode searches. The key takeaways are:
- Event handling gives you visibility into the document processing workflow, which is crucial for user experience and debugging
- Proper configuration of search options can dramatically improve performance and accuracy
- Error handling and resource management are critical for production applications
- Real-world implementation often requires additional considerations like async patterns, caching, and integration with larger application architectures
The next step is to take these concepts and apply them to your specific use case. Start with simple scenarios and gradually add complexity as you become more comfortable with the library.
Remember, the GroupDocs.Signature documentation is your friend for diving deeper into specific features, and the community forums are great for getting help with specific issues.
Frequently Asked Questions
Q: Can I cancel a search operation once it’s started? A: GroupDocs.Signature doesn’t provide built-in cancellation, but you can implement timeout logic or use CancellationTokens if you wrap the operations in async methods.
Q: How do I handle documents that don’t have any barcodes? A: Your search will simply return an empty list. Always check the count of results before processing them, and decide how your application should handle this scenario.
Q: What’s the difference between searching for barcode signatures vs. other signature types?
A: The process is similar, but you use different search option classes (BarcodeSearchOptions, TextSearchOptions, etc.) and search for different signature types (BarcodeSignature, TextSignature, etc.).
Q: Can I search for multiple barcode patterns in a single operation? A: Not directly, but you can perform multiple searches with different options, or use broader search criteria and filter the results afterward.
Q: How do I handle very large documents without running out of memory? A: Process documents in smaller chunks (by page ranges), use proper disposal patterns, and consider implementing streaming approaches for very large files.
Q: Is it possible to modify barcodes once I find them? A: GroupDocs.Signature is primarily for reading and verifying signatures. For modification, you’d typically need to use it in conjunction with other document manipulation libraries.
Q: What file formats are supported? A: GroupDocs.Signature supports a wide range of formats including PDF, Word, Excel, PowerPoint, and many image formats. Check the official documentation for the complete list.
Q: How do I handle password-protected documents?
A: You can pass the password when creating the Signature object: new Signature(filePath, new LoadOptions() { Password = "your_password" }).
Additional Resources
- Documentation: https://docs.groupdocs.com/signature/net/
- API Reference: https://reference.groupdocs.com/signature/net
