using System;
using System.Drawing;
using Vintasoft.Barcode;
            
/// <summary>
/// Test that shows how to set the delegate for barcode verification and
/// verify found barcodes during the barcode recognition process.
/// </summary>
class UserDefinedChecksumExample
{
    /// <summary>
    /// Runs the test.
    /// </summary>
    public static void Run()
    {
        string value = "1234567890AbC";
            
        // create the barcode writer
        BarcodeWriter writer = new BarcodeWriter();
        // specify that writer must generate Code39 barcode
        writer.Settings.Barcode = BarcodeType.Code39;
            
        // create the barcode reader
        using (BarcodeReader reader = new BarcodeReader())
        {
            // specify that reader must search for Code39 barcodes only
            reader.Settings.ScanBarcodeTypes = BarcodeType.Code39;
            // specify that reader must search for barcode with 100% confidence only
            reader.Settings.MinConfidence = 100;
            // specify that reader must use barcodes in automatic mode
            reader.Settings.AutomaticRecognition = true;
            // specify that reader must search for 1 barcode
            reader.Settings.ExpectedBarcodes = 1;
            
            // set the barcode value without checksum
            writer.Settings.Value = value;
            // create image with barcode without checksum
            using (Image barcodeNoChecksumImage = writer.GetBarcodeAsBitmap())
            {
                // set the barcode value with checksum
                writer.Settings.Value = value + GenerateChecksum(value);
                // create image with barcode with checksum
                using (Image barcodeWithMyChecksumImage = writer.GetBarcodeAsBitmap())
                {
                    // specify delegate to a method for barcode verification
                    reader.Settings.VerifyBarcodeMethod = VerifyBarcodeMethod;
            
                    // read barcodes from barcode image without checksum,
                    // barcode reader will not find barcode
                    IBarcodeInfo[] infos = reader.ReadBarcodes(barcodeNoChecksumImage);
                    Console.WriteLine("Scan (NoChecksum):");
                    for (int i = 0; i < infos.Length; i++)
                        Console.WriteLine(infos[i].Value);
            
                    // read barcodes from barcode image with checksum,
                    // barcode reader will find 1 barcode
                    infos = reader.ReadBarcodes(barcodeWithMyChecksumImage);
                    Console.WriteLine("Scan (MyChecksum):");
                    for (int i = 0; i < infos.Length; i++)
                        Console.WriteLine(infos[i].Value);
                }
            }
        }
    }
            
    /// <summary>
    /// Generates checksum modulo 1000.
    /// </summary>
    static string GenerateChecksum(string value)
    {
        int checkSum = 0;
        for (int i = 0; i < value.Length; i++)
        {
            checkSum += ((byte)value[i]) * (i + 1);
            checkSum %= 1000;
        }
        // result - [000..999]
        return checkSum.ToString().PadLeft(3, '0');
    }
            
    /// <summary>
    /// Verifies the barcode during the barcode recognition process.
    /// </summary>
    static void VerifyBarcodeMethod(BarcodeReader reader, IBarcodeInfo barcodeInfo)
    {
        if (TestChecksum(barcodeInfo.Value))
            barcodeInfo.Confidence = 100;
        else
            barcodeInfo.Confidence = 0;
    }
            
    /// <summary>
    /// Tests checksum in barcode value.
    /// </summary>
    static bool TestChecksum(string barcodeValue)
    {
        string value = barcodeValue.Substring(0, barcodeValue.Length - 3);
        string readChecksum = barcodeValue.Substring(barcodeValue.Length - 3);
        return readChecksum == GenerateChecksum(value);
    }
            
}

/// <summary>
/// Verifies the barcode during the barcode recognition process.
/// </summary>
static void VerifyBarcodeMethod(BarcodeReader reader, IBarcodeInfo barcodeInfo)
{
    if (barcodeInfo.ReadingQuality < 0.2)
        barcodeInfo.Confidence = 0;
}
            
// ...
// reader.Settings.VerifyBarcodeMethod = VerifyBarcodeMethod;
// ...