How to Use Async and Multithreading for QR Code Operations in C#

using IronQr;
using IronQr.Enum;
using IronSoftware.Drawing;

// --- Async read: non-blocking QR decode ---
var inputBmp = AnyBitmap.FromFile("event-badge.png");
var imageInput = new QrImageInput(inputBmp, QrScanMode.OnlyDetectionModel);

var reader = new QrReader();
IEnumerable<QrResult> results = await reader.ReadAsync(imageInput);

foreach (QrResult result in results)
{
    Console.WriteLine($"[{result.QrType}] {result.Value}");
}

// --- Async-wrapped save: QrWriter.Write() and QrCode.Save() are synchronous ---
QrCode qrCode = QrWriter.Write("https://ironsoftware.com");
AnyBitmap qrImage = qrCode.Save();

// Save the bitmap bytes asynchronously (not an IronQR API — standard .NET async I/O)
byte[] pngBytes = qrImage.ExportBytes();
await File.WriteAllBytesAsync("output-qr.png", pngBytes);

Imports IronQr
Imports IronQr.Enum
Imports IronSoftware.Drawing
Imports System.IO

' --- Async read: non-blocking QR decode ---
Dim inputBmp = AnyBitmap.FromFile("event-badge.png")
Dim imageInput = New QrImageInput(inputBmp, QrScanMode.OnlyDetectionModel)

Dim reader = New QrReader()
Dim results As IEnumerable(Of QrResult) = Await reader.ReadAsync(imageInput)

For Each result As QrResult In results
    Console.WriteLine($"[{result.QrType}] {result.Value}")
Next

' --- Async-wrapped save: QrWriter.Write() and QrCode.Save() are synchronous ---
Dim qrCode As QrCode = QrWriter.Write("https://ironsoftware.com")
Dim qrImage As AnyBitmap = qrCode.Save()

' Save the bitmap bytes asynchronously (not an IronQR API — standard .NET async I/O)
Dim pngBytes As Byte() = qrImage.ExportBytes()
Await File.WriteAllBytesAsync("output-qr.png", pngBytes)

using IronQr;
using IronQr.Enum;
using IronSoftware.Drawing;
using System.Collections.Concurrent;
using System.Diagnostics;

string[] files = Directory.GetFiles("qr-images/", "*.png");
var allResults = new ConcurrentBag<(string File, string Value)>();
int failCount = 0;
var sw = Stopwatch.StartNew();

Parallel.ForEach(files, new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount }, file =>
{
    try
    {
        var input = new QrImageInput(
            AnyBitmap.FromFile(file),
            QrScanMode.OnlyDetectionModel);

        // Per-thread QrReader instance — safe default
        var results = new QrReader().Read(input);

        foreach (QrResult result in results)
        {
            allResults.Add((Path.GetFileName(file), result.Value));
        }
    }
    catch (Exception ex)
    {
        Interlocked.Increment(ref failCount);
        Console.Error.WriteLine($"[ERROR] {Path.GetFileName(file)}: {ex.Message}");
    }
});

sw.Stop();

Console.WriteLine($"Processed {files.Length} files in {sw.Elapsed.TotalSeconds:F1}s");
Console.WriteLine($"QR codes found: {allResults.Count} | Failures: {failCount}");
Console.WriteLine($"Throughput: {files.Length / sw.Elapsed.TotalSeconds:F1} files/sec");

Imports IronQr
Imports IronQr.Enum
Imports IronSoftware.Drawing
Imports System.Collections.Concurrent
Imports System.Diagnostics

Dim files As String() = Directory.GetFiles("qr-images/", "*.png")
Dim allResults As New ConcurrentBag(Of (File As String, Value As String))()
Dim failCount As Integer = 0
Dim sw As Stopwatch = Stopwatch.StartNew()

Parallel.ForEach(files, New ParallelOptions With {.MaxDegreeOfParallelism = Environment.ProcessorCount}, Sub(file)
    Try
        Dim input As New QrImageInput(AnyBitmap.FromFile(file), QrScanMode.OnlyDetectionModel)

        ' Per-thread QrReader instance — safe default
        Dim results = New QrReader().Read(input)

        For Each result As QrResult In results
            allResults.Add((Path.GetFileName(file), result.Value))
        Next
    Catch ex As Exception
        Interlocked.Increment(failCount)
        Console.Error.WriteLine($"[ERROR] {Path.GetFileName(file)}: {ex.Message}")
    End Try
End Sub)

sw.Stop()

Console.WriteLine($"Processed {files.Length} files in {sw.Elapsed.TotalSeconds:F1}s")
Console.WriteLine($"QR codes found: {allResults.Count} | Failures: {failCount}")
Console.WriteLine($"Throughput: {files.Length / sw.Elapsed.TotalSeconds:F1} files/sec")

using IronQr;
using IronQr.Enum;
using IronSoftware.Drawing;
using System.Collections.Concurrent;
using System.Diagnostics;

string[] files = Directory.GetFiles("high-volume/", "*.png");
var results = new ConcurrentBag<(string File, string Value)>();
int maxConcurrency = Environment.ProcessorCount;
using var semaphore = new SemaphoreSlim(maxConcurrency);
var sw = Stopwatch.StartNew();

var tasks = files.Select(async file =>
{
    await semaphore.WaitAsync();
    try
    {
        var bmp = AnyBitmap.FromFile(file);
        // OnlyDetectionModel: fastest per-image — critical at scale
        var input = new QrImageInput(bmp, QrScanMode.OnlyDetectionModel);
        var qrResults = await new QrReader().ReadAsync(input);

        foreach (var qr in qrResults)
        {
            results.Add((Path.GetFileName(file), qr.Value));
        }
    }
    catch (Exception ex)
    {
        Console.Error.WriteLine($"{{\"file\":\"{Path.GetFileName(file)}\",\"error\":\"{ex.Message}\"}}");
    }
    finally
    {
        semaphore.Release();
    }
});

await Task.WhenAll(tasks);
sw.Stop();

Console.WriteLine($"Pipeline complete: {results.Count} QR codes from {files.Length} files in {sw.Elapsed.TotalSeconds:F1}s");

Imports IronQr
Imports IronQr.Enum
Imports IronSoftware.Drawing
Imports System.Collections.Concurrent
Imports System.Diagnostics

Module Program
    Sub Main()
        Dim files As String() = Directory.GetFiles("high-volume/", "*.png")
        Dim results As New ConcurrentBag(Of (File As String, Value As String))()
        Dim maxConcurrency As Integer = Environment.ProcessorCount
        Using semaphore As New SemaphoreSlim(maxConcurrency)
            Dim sw As Stopwatch = Stopwatch.StartNew()

            Dim tasks = files.Select(Function(file) Task.Run(Async Function()
                                                                  Await semaphore.WaitAsync()
                                                                  Try
                                                                      Dim bmp = AnyBitmap.FromFile(file)
                                                                      ' OnlyDetectionModel: fastest per-image — critical at scale
                                                                      Dim input As New QrImageInput(bmp, QrScanMode.OnlyDetectionModel)
                                                                      Dim qrResults = Await (New QrReader()).ReadAsync(input)

                                                                      For Each qr In qrResults
                                                                          results.Add((Path.GetFileName(file), qr.Value))
                                                                      Next
                                                                  Catch ex As Exception
                                                                      Console.Error.WriteLine($"{{""file"":""{Path.GetFileName(file)}"",""error"":""{ex.Message}""}}")
                                                                  Finally
                                                                      semaphore.Release()
                                                                  End Try
                                                              End Function))

            Task.WhenAll(tasks).Wait()
            sw.Stop()

            Console.WriteLine($"Pipeline complete: {results.Count} QR codes from {files.Length} files in {sw.Elapsed.TotalSeconds:F1}s")
        End Using
    End Sub
End Module