How to Validate Barcode Checksums and Use Format-Aware Reading in C#

using IronBarCode;

// Constrain reads to 1D formats and enable secondary verification.
// ConfidenceThreshold rejects decodes where the ML detector falls below 85%,
// acting as a quality gate for optional-checksum symbologies like Code39.
var options = new BarcodeReaderOptions
{
    ExpectBarcodeTypes  = BarcodeEncoding.AllOneDimensional,
    RemoveFalsePositive = true,
    ConfidenceThreshold = 0.85,
    Speed               = ReadingSpeed.Detailed
};

BarcodeResults results = BarcodeReader.Read("warehouse-rack.png", options);

foreach (BarcodeResult result in results)
{
    // Each result has passed checksum validation (mandatory formats)
    // and the 85% confidence threshold, so no additional filtering is needed.
    Console.WriteLine($"[{result.BarcodeType}] {result.Value}  page={result.PageNumber}");
}

if (results.Count == 0)
{
    Console.Error.WriteLine("No valid barcodes found. Possible causes:");
    Console.Error.WriteLine("  - Check digit mismatch (barcode silently rejected)");
    Console.Error.WriteLine("  - Confidence below 85% threshold");
    Console.Error.WriteLine("  - Format not in ExpectBarcodeTypes");
}

using IronBarCode;

// Constrained read: only Code128 barcodes are returned.
// Faster because the reader skips all other format detectors.
var constrainedOptions = new BarcodeReaderOptions
{
    ExpectBarcodeTypes     = BarcodeEncoding.Code128,
    Speed                  = ReadingSpeed.Faster,
    ExpectMultipleBarcodes = false
};

// Broad read: all supported formats are scanned.
// Useful for verification or when the image format is unknown.
var broadOptions = new BarcodeReaderOptions
{
    ExpectBarcodeTypes     = BarcodeEncoding.All,
    Speed                  = ReadingSpeed.Detailed,
    ExpectMultipleBarcodes = true
};

string imagePath = "shipping-label.png";

BarcodeResults constrained = BarcodeReader.Read(imagePath, constrainedOptions);
Console.WriteLine($"Constrained: {constrained.Count} Code128 barcode(s) found");

BarcodeResults broad = BarcodeReader.Read(imagePath, broadOptions);
Console.WriteLine($"Broad: {broad.Count} barcode(s) found across all formats");

foreach (BarcodeResult result in broad)
{
    Console.WriteLine($"  [{result.BarcodeType}] {result.Value}");
}

using IronBarCode;

// Layered validation for retail POS: EAN-13, UPC-A, and UPC-E only.
// Each property adds a distinct filter to the read pipeline.
var options = new BarcodeReaderOptions
{
    // Layer 1: format constraint, accept only retail symbologies
    ExpectBarcodeTypes = BarcodeEncoding.EAN13 | BarcodeEncoding.UPCA | BarcodeEncoding.UPCE,

    // Layer 2: confidence threshold, reject decodes below 80%
    ConfidenceThreshold = 0.8,

    // Layer 3: false-positive removal, runs a secondary verification pass
    RemoveFalsePositive = true,

    Speed                  = ReadingSpeed.Balanced,
    ExpectMultipleBarcodes = false,

    // Require 3 agreeing scan lines to reduce phantom reads from noisy images
    MinScanLines = 3
};

string[] scanFiles = Directory.GetFiles("pos-scans/", "*.png");

foreach (string file in scanFiles)
{
    BarcodeResults results = BarcodeReader.Read(file, options);

    if (results.Count == 0)
    {
        // No barcode passed all validation layers
        Console.Error.WriteLine($"REJECT {Path.GetFileName(file)}: "
            + "no valid EAN-13/UPC barcode (checksum, confidence, or format mismatch)");
        continue;
    }

    BarcodeResult primary = results.First();

    // Post-read assertion: verify the decoded format matches expectations.
    // ExpectBarcodeTypes already constrains the reader; this check documents
    // intent and surfaces unexpected results during future changes.
    if (primary.BarcodeType != BarcodeEncoding.EAN13
        && primary.BarcodeType != BarcodeEncoding.UPCA
        && primary.BarcodeType != BarcodeEncoding.UPCE)
    {
        Console.Error.WriteLine($"UNEXPECTED FORMAT {Path.GetFileName(file)}: "
            + $"got {primary.BarcodeType}, expected EAN-13/UPC");
        continue;
    }

    Console.WriteLine($"OK {Path.GetFileName(file)}: [{primary.BarcodeType}] {primary.Value}");
}